Acceptability judgments are reports of a speaker’s or signer’s subjective sense of the well-formedness, nativeness, or naturalness of (novel) linguistic forms. Their value comes in providing data about the nature of the human capacity to generalize beyond linguistic forms previously encountered in language comprehension. For this reason, acceptability judgments are often also called grammaticality judgments (particularly in syntax), although unlike the theory-dependent notion of grammaticality, acceptability is accessible to consciousness. While acceptability judgments have been used to test grammatical claims since ancient times, they became particularly prominent with the birth of generative syntax. Today they are also widely used in other linguistic schools (e.g., cognitive linguistics) and other linguistic domains (pragmatics, semantics, morphology, and phonology), and have been applied in a typologically diverse range of languages. As psychological responses to linguistic stimuli, acceptability judgments are experimental data. Their value thus depends on the validity of the experimental procedures, which, in their traditional version (where theoreticians elicit judgments from themselves or a few colleagues), have been criticized as overly informal and biased. Traditional responses to such criticisms have been supplemented in recent years by laboratory experiments that use formal psycholinguistic methods to collect and quantify judgments from nonlinguists under controlled conditions. Such formal experiments have played an increasingly influential role in theoretical linguistics, being used to justify subtle judgment claims or new grammatical models that incorporate gradience or lexical influences. They have also been used to probe the cognitive processes giving rise to the sense of acceptability itself, the central finding being that acceptability reflects processing ease. Exploring what this finding means will require not only further empirical work on the acceptability judgment process, but also theoretical work on the nature of grammar.
Clinical linguistics is the branch of linguistics that applies linguistic concepts and theories to the study of language disorders. As the name suggests, clinical linguistics is a dual-facing discipline. Although the conceptual roots of this field are in linguistics, its domain of application is the vast array of clinical disorders that may compromise the use and understanding of language. Both dimensions of clinical linguistics can be addressed through an examination of specific linguistic deficits in individuals with neurodevelopmental disorders, craniofacial anomalies, adult-onset neurological impairments, psychiatric disorders, and neurodegenerative disorders. Clinical linguists are interested in the full range of linguistic deficits in these conditions, including phonetic deficits of children with cleft lip and palate, morphosyntactic errors in children with specific language impairment, and pragmatic language impairments in adults with schizophrenia.
Like many applied disciplines in linguistics, clinical linguistics sits at the intersection of a number of areas. The relationship of clinical linguistics to the study of communication disorders and to speech-language pathology (speech and language therapy in the United Kingdom) are two particularly important points of intersection. Speech-language pathology is the area of clinical practice that assesses and treats children and adults with communication disorders. All language disorders restrict an individual’s ability to communicate freely with others in a range of contexts and settings. So language disorders are first and foremost communication disorders. To understand language disorders, it is useful to think of them in terms of points of breakdown on a communication cycle that tracks the progress of a linguistic utterance from its conception in the mind of a speaker to its comprehension by a hearer. This cycle permits the introduction of a number of important distinctions in language pathology, such as the distinction between a receptive and an expressive language disorder, and between a developmental and an acquired language disorder. The cycle is also a useful model with which to conceptualize a range of communication disorders other than language disorders. These other disorders, which include hearing, voice, and fluency disorders, are also relevant to clinical linguistics.
Clinical linguistics draws on the conceptual resources of the full range of linguistic disciplines to describe and explain language disorders. These disciplines include phonetics, phonology, morphology, syntax, semantics, pragmatics, and discourse. Each of these linguistic disciplines contributes concepts and theories that can shed light on the nature of language disorder. A wide range of tools and approaches are used by clinical linguists and speech-language pathologists to assess, diagnose, and treat language disorders. They include the use of standardized and norm-referenced tests, communication checklists and profiles (some administered by clinicians, others by parents, teachers, and caregivers), and qualitative methods such as conversation analysis and discourse analysis. Finally, clinical linguists can contribute to debates about the nosology of language disorders. In order to do so, however, they must have an understanding of the place of language disorders in internationally recognized classification systems such as the 2013 Diagnostic and Statistical Manual of Mental Disorders (DSM-5) of the American Psychiatric Association.
Morphological defectiveness refers to situations where one or more paradigmatic forms of a lexeme are not realized, without plausible syntactic, semantic, or phonological causes. The phenomenon tends to be associated with low-frequency lexemes and loanwords. Typically, defectiveness is gradient, lexeme-specific, and sensitive to the internal structure of paradigms.
The existence of defectiveness is a challenge to acquisition models and morphological theories where there are elsewhere operations to materialize items. For this reason, defectiveness has become a rich field of research in recent years, with distinct approaches that view it as an item-specific idiosyncrasy, as an epiphenomenal result of rule competition, or as a normal morphological alternation within a paradigmatic space.
Derivational morphology is a type of word formation that creates new lexemes, either by changing syntactic category or by adding substantial new meaning (or both) to a free or bound base. Derivation may be contrasted with inflection on the one hand or with compounding on the other. The distinctions between derivation and inflection and between derivation and compounding, however, are not always clear-cut. New words may be derived by a variety of formal means including affixation, reduplication, internal modification of various sorts, subtraction, and conversion. Affixation is best attested cross-linguistically, especially prefixation and suffixation. Reduplication is also widely found, with various internal changes like ablaut and root and pattern derivation less common. Derived words may fit into a number of semantic categories. For nouns, event and result, personal and participant, collective and abstract noun are frequent. For verbs, causative and applicative categories are well-attested, as are relational and qualitative derivations for adjectives. Languages frequently also have ways of deriving negatives, relational words, and evaluatives. Most languages have derivation of some sort, although there are languages that rely more heavily on compounding than on derivation to build their lexical stock. A number of topics have dominated the theoretical literature on derivation, including productivity (the extent to which new words can be created with a given affix or morphological process), the principles that determine the ordering of affixes, and the place of derivational morphology with respect to other components of the grammar. The study of derivation has also been important in a number of psycholinguistic debates concerning the perception and production of language.
In the Early Modern English period (1500–1700), steps were taken toward Standard English, and this was also the time when Shakespeare wrote, but these perspectives are only part of the bigger picture. This chapter looks at Early Modern English as a variable and changing language not unlike English today. Standardization is found particularly in spelling, and new vocabulary was created as a result of the spread of English into various professional and occupational specializations. New research using digital corpora, dictionaries, and databases reveals the gradual nature of these processes. Ongoing developments were no less gradual in pronunciation, with processes such as the Great Vowel Shift, or in grammar, where many changes resulted in new means of expression and greater transparency. Word order was also subject to gradual change, becoming more fixed over time.
Holger Diessel and Martin Hilpert
Until recently, theoretical linguists have paid little attention to the frequency of linguistic elements in grammar and grammatical development. It is a standard assumption of (most) grammatical theories that the study of grammar (or competence) must be separated from the study of language use (or performance). However, this view of language has been called into question by various strands of research that have emphasized the importance of frequency for the analysis of linguistic structure. In this research, linguistic structure is often characterized as an emergent phenomenon shaped by general cognitive processes such as analogy, categorization, and automatization, which are crucially influenced by frequency of occurrence.
There are many different ways in which frequency affects the processing and development of linguistic structure. Historical linguists have shown that frequent strings of linguistic elements are prone to undergo phonetic reduction and coalescence, and that frequent expressions and constructions are more resistant to structure mapping and analogical leveling than infrequent ones. Cognitive linguists have argued that the organization of constituent structure and embedding is based on the language users’ experience with linguistic sequences, and that the productivity of grammatical schemas or rules is determined by the combined effect of frequency and similarity. Child language researchers have demonstrated that frequency of occurrence plays an important role in the segmentation of the speech stream and the acquisition of syntactic categories, and that the statistical properties of the ambient language are much more regular than commonly assumed. And finally, psycholinguists have shown that structural ambiguities in sentence processing can often be resolved by lexical and structural frequencies, and that speakers’ choices between alternative constructions in language production are related to their experience with particular linguistic forms and meanings. Taken together, this research suggests that our knowledge of grammar is grounded in experience.
Linguistic change not only affects the lexicon and the phonology of words, it also operates on the grammar of a language. In this context, grammaticalization is concerned with the development of lexical items into markers of grammatical categories or, more generally, with the development of markers used for procedural cueing of abstract relationships out of linguistic items with concrete referential meaning. A well-known example is the English verb go in its function of a future marker, as in She is going to visit her friend. Phenomena like these are very frequent across the world’s languages and across many different domains of grammatical categories. In the last 50 years, research on grammaticalization has come up with a plethora of (a) generalizations, (b) models of how grammaticalization works, and (c) methodological refinements.
On (a): Processes of grammaticalization develop gradually, step by step, and the sequence of the individual stages follows certain clines as they have been generalized from cross-linguistic comparison (unidirectionality). Even though there are counterexamples that go against the directionality of various clines, their number seems smaller than assumed in the late 1990s.
On (b): Models or scenarios of grammaticalization integrate various factors. Depending on the theoretical background, grammaticalization and its results are motivated either by the competing motivations of economy vs. iconicity/explicitness in functional typology or by a change from movement to merger in the minimalist program. Pragmatic inference is of central importance for initiating processes of grammaticalization (and maybe also at later stages), and it activates mechanisms like reanalysis and analogy, whose status is controversial in the literature. Finally, grammaticalization does not only work within individual languages/varieties, it also operates across languages. In situations of contact, the existence of a certain grammatical category may induce grammaticalization in another language.
On (c): Even though it is hard to measure degrees of grammaticalization in terms of absolute and exact figures, it is possible to determine relative degrees of grammaticalization in terms of the autonomy of linguistic signs. Moreover, more recent research has come up with criteria for distinguishing grammaticalization and lexicalization (defined as the loss of productivity, transparency, and/or compositionality of former productive, transparent, and compositional structures).
In spite of these findings, there are still quite a number of questions that need further research. Two questions to be discussed address basic issues concerning the overall properties of grammaticalization. (1) What is the relation between constructions and grammaticalization? In the more traditional view, constructions are seen as the syntactic framework within which linguistic items are grammaticalized. In more recent approaches based on construction grammar, constructions are defined as combinations of form and meaning. Thus, grammaticalization can be seen in the light of constructionalization, i.e., the creation of new combinations of form and meaning. Even though constructionalization covers many apects of grammaticalization, it does not exhaustively cover the domain of grammaticalization. (2) Is grammaticalization cross-linguistically homogeneous, or is there a certain range of variation? There is evidence from East and mainland Southeast Asia that there is cross-linguistic variation to some extent.
Irit Meir and Oksana Tkachman
Iconicity is a relationship of resemblance or similarity between the two aspects of a sign: its form and its meaning. An iconic sign is one whose form resembles its meaning in some way. The opposite of iconicity is arbitrariness. In an arbitrary sign, the association between form and meaning is based solely on convention; there is nothing in the form of the sign that resembles aspects of its meaning. The Hindu-Arabic numerals 1, 2, 3 are arbitrary, because their current form does not correlate to any aspect of their meaning. In contrast, the Roman numerals I, II, III are iconic, because the number of occurrences of the sign I correlates with the quantity that the numerals represent. Because iconicity has to do with the properties of signs in general and not only those of linguistic signs, it plays an important role in the field of semiotics—the study of signs and signaling. However, language is the most pervasive symbolic communicative system used by humans, and the notion of iconicity plays an important role in characterizing the linguistic sign and linguistic systems. Iconicity is also central to the study of literary uses of language, such as prose and poetry.
There are various types of iconicity: the form of a sign may resemble aspects of its meaning in several ways: it may create a mental image of the concept (imagic iconicity), or its structure and the arrangement of its elements may resemble the structural relationship between components of the concept represented (diagrammatic iconicity). An example of the first type is the word cuckoo, whose sounds resemble the call of the bird, or a sign such as RABBIT in Israeli Sign Language, whose form—the hands representing the rabbit's long ears—resembles a visual property of that animal. An example of diagrammatic iconicity is vēnī, vīdī, vīcī, where the order of clauses in a discourse is understood as reflecting the sequence of events in the world.
Iconicity is found on all linguistic levels: phonology, morphology, syntax, semantics, and discourse. It is found both in spoken languages and in sign languages. However, sign languages, because of the visual-gestural modality through which they are transmitted, are much richer in iconic devices, and therefore offer a rich array of topics and perspectives for investigating iconicity, and the interaction between iconicity and language structure.
The Kiowa-Tanoan family is a small group of Native American languages of the Plains and pueblo Southwest. It comprises Kiowa, of the eponymous Plains tribe, and the pueblo-based Tanoan languages, Jemez (Towa), Tewa, and Northern and Southern Tiwa. These free-word-order languages display a number of typologically unusual characteristics that have rightly attracted attention within a range of subdisciplines and theories.
One word of Taos (my construction based on Kontak and Kunkel’s work) illustrates. In tóm-múlu-wia ‘I gave him/her a drum,’ the verb wia ‘gave’ obligatorily incorporates its object, múlu ‘drum.’ The agreement prefix tóm encodes not only object number, but identities of agent and recipient as first and third singular, respectively, and this all in a single syllable. Moreover, the object number here is not singular, but “inverse”: singular for some nouns, plural for others (tóm-músi-wia only has the plural object reading ‘I gave him/her cats’).
This article presents a comparative overview of the three areas just illustrated: from morphosemantics, inverse marking and noun class; from morphosyntax, super-rich fusional agreement; and from syntax, incorporation. The second of these also touches on aspects of morphophonology, the family’s three-tone system and its unusually heavy grammatical burden, and on further syntax, obligatory passives. Together, these provide a wide window on the grammatical wealth of this fascinating family.
Young-mee Yu Cho
Due to a number of unusual and interesting properties, Korean phonetics and phonology have been generating productive discussion within modern linguistic theories, starting from structuralism, moving to classical generative grammar, and more recently to post-generative frameworks of Autosegmental Theory, Government Phonology, Optimality Theory, and others. In addition, it has been discovered that a description of important issues of phonology cannot be properly made without referring to the interface between phonetics and phonology on the one hand, and phonology and morpho-syntax on the other. Some phonological issues from Standard Korean are still under debate and will likely be of value in helping to elucidate universal phonological properties with regard to phonation contrast, vowel and consonant inventories, consonantal markedness, and the motivation for prosodic organization in the lexicon.
As might be expected from the difficulty of traversing it, the Sahara Desert has been a fairly effective barrier to direct contact between its two edges; trans-Saharan language contact is limited to the borrowing of non-core vocabulary, minimal from south to north and mostly mediated by education from north to south. Its own inhabitants, however, are necessarily accustomed to travelling desert spaces, and contact between languages within the Sahara has often accordingly had a much greater impact. Several peripheral Arabic varieties of the Sahara retain morphology as well as vocabulary from the languages spoken by their speakers’ ancestors, in particular Berber in the southwest and Beja in the southeast; the same is true of at least one Saharan Hausa variety. The Berber languages of the northern Sahara have in turn been deeply affected by centuries of bilingualism in Arabic, borrowing core vocabulary and some aspects of morphology and syntax. The Northern Songhay languages of the central Sahara have been even more profoundly affected by a history of multilingualism and language shift involving Tuareg, Songhay, Arabic, and other Berber languages, much of which remains to be unraveled. These languages have borrowed so extensively that they retain barely a few hundred core words of Songhay vocabulary; those loans have not only introduced new morphology but in some cases replaced old morphology entirely. In the southeast, the spread of Arabic westward from the Nile Valley has created a spectrum of varieties with varying degrees of local influence; the Saharan ones remain almost entirely undescribed. Much work remains to be done throughout the region, not only on identifying and analyzing contact effects but even simply on describing the languages its inhabitants speak.
Nora C. England
Mayan languages are spoken by over 5 million people in Guatemala, Mexico, Belize, and Honduras. There are around 30 different languages today, ranging in size from fairly large (about a million speakers) to very small (fewer than 30 speakers). All Mayan languages are endangered given that at least some children in some communities are not learning the language, and two languages have disappeared since European contact. Mayas developed the most elaborated and most widely attested writing system in the Americas (starting about 300 BC).
The sounds of Mayan languages consist of a voiceless stop and affricate series with corresponding glottalized stops (either implosive and ejective) and affricates, glottal stop, voiceless fricatives (including h in some of them inherited from Proto-Maya), two to three nasals, three to four approximants, and a five vowel system with contrasting vowel length (or tense/lax distinctions) in most languages. Several languages have developed contrastive tone.
The major word classes in Mayan languages include nouns, verbs, adjectives, positionals, and affect words. The difference between transitive verbs and intransitive verbs is rigidly maintained in most languages. They usually use the same aspect markers (but not always). Intransitive verbs only indicate their subjects while transitive verbs indicate both subjects and objects. Some languages have a set of status suffixes which is different for the two classes. Positionals are a root class whose most characteristic word form is a non-verbal predicate. Affect words indicate impressions of sounds, movements, and activities. Nouns have a number of different subclasses defined on the basis of characteristics when possessed, or the structure of compounds. Adjectives are formed from a small class of roots (under 50) and many derived forms from verbs and positionals.
Predicate types are transitive, intransitive, and non-verbal. Non-verbal predicates are based on nouns, adjectives, positionals, numbers, demonstratives, and existential and locative particles. They are distinct from verbs in that they do not take the usual verbal aspect markers. Mayan languages are head marking and verb initial; most have VOA flexible order but some have VAO rigid order. They are morphologically ergative and also have at least some rules that show syntactic ergativity. The most common of these is a constraint on the extraction of subjects of transitive verbs (ergative) for focus and/or interrogation, negation, or relativization. In addition, some languages make a distinction between agentive and non-agentive intransitive verbs. Some also can be shown to use obviation and inverse as important organizing principles. Voice categories include passive, antipassive and agent focus, and an applicative with several different functions.
Phonotactics is the study of restrictions on possible sound sequences in a language. In any language, some phonotactic constraints can be stated without reference to morphology, but many of the more nuanced phonotactic generalizations do make use of morphosyntactic and lexical information. At the most basic level, many languages mark edges of words in some phonological way. Different phonotactic constraints hold of sounds that belong to the same morpheme as opposed to sounds that are separated by a morpheme boundary. Different phonotactic constraints may apply to morphemes of different types (such as roots versus affixes). There are also correlations between phonotactic shapes and following certain morphosyntactic and phonological rules, which may correlate to syntactic category, declension class, or etymological origins.
Approaches to the interaction between phonotactics and morphology address two questions: (1) how to account for rules that are sensitive to morpheme boundaries and structure and (2) determining the status of phonotactic constraints associated with only some morphemes. Theories differ as to how much morphological information phonology is allowed to access. In some theories of phonology, any reference to the specific identities or subclasses of morphemes would exclude a rule from the domain of phonology proper. These rules are either part of the morphology or are not given the status of a rule at all. Other theories allow the phonological grammar to refer to detailed morphological and lexical information. Depending on the theory, phonotactic differences between morphemes may receive direct explanations or be seen as the residue of historical change and not something that constitutes grammatical knowledge in the speaker’s mind.
It has been an ongoing issue within generative linguistics how to properly analyze morpho-phonological processes. Morpho-phonological processes typically have exceptions, but nonetheless they are often productive. Such productive, but exceptionful, processes are difficult to analyze, since grammatical rules or constraints are normally invoked in the analysis of a productive pattern, whereas exceptions undermine the validity of the rules and constraints. In addition, productivity of a morpho-phonological process may be gradient, possibly reflecting the relative frequency of the relevant pattern in the lexicon. Simple lexical listing of exceptions as suppletive forms would not be sufficient to capture such gradient productivity of a process with exceptions. It is then necessary to posit grammatical rules or constraints even for exceptionful processes as long as they are at least in part productive. Moreover, the productivity can be correctly estimated only when the domain of rule application is correctly identified. Consequently, a morpho-phonological process cannot be properly analyzed unless we possess both the correct description of its application conditions and the appropriate stochastic grammatical mechanisms to capture its productivity.
The same issues arise in the analysis of morpho-phonological processes in Korean, in particular, n-insertion, sai-siot, and vowel harmony. Those morpho-phonological processes have many exceptions and variations, which make them look quite irregular and unpredictable. However, they have at least a certain degree of productivity. Moreover, the variable application of each process is still systematic in that various factors, phonological, morphosyntactic, sociolinguistic, and processing, contribute to the overall probability of rule application. Crucially, grammatical rules and constraints, which have been proposed within generative linguistics to analyze categorical and exceptionless phenomena, may form an essential part of the analysis of the morpho-phonological processes in Korean.
For an optimal analysis of each of the morpho-phonological processes in Korean, the correct conditions and domains for its application need to be identified first, and its exact productivity can then be measured. Finally, the appropriate stochastic grammatical mechanisms need to be found or developed in order to capture the measured productivity.
Within the Ryukyuan branch of the Japonic family of languages, present-day Okinawan retains numerous regional variants which have evolved for over a thousand years in the Ryukyuan Archipelago. Okinawan is one of the six Ryukyuan languages that UNESCO identified as endangered. One of the theoretically fascinating features is that there is substantial evidence for establishing a high central phonemic vowel in Okinawan although there is currently no overt surface [ï]. Moreover, the word-initial glottal stop [ʔ] in Okinawan is more salient than that in Japanese when followed by vowels, enabling recognition that all Okinawan words are consonant-initial. Except for a few particles, all Okinawan words are composed of two or more morae. Suffixation or vowel lengthening (on nouns, verbs, and adjectives) provides the means for signifying persons as well as things related to human consumption or production. Every finite verb in Okinawan terminates with a mood element. Okinawan exhibits a complex interplay of mood or negative elements and focusing particles. Evidentiality is also realized as an obligatory verbal suffix.
Old and Middle Japanese are the pre-modern periods of the attested history of the Japanese language. Old Japanese (OJ) is largely the language of the 8th century, with a modest, but still significant number of written sources, most of which is poetry. Middle Japanese is divided into two distinct periods, Early Middle Japanese (EMJ, 800–1200) and Late Middle Japanese (LMJ, 1200–1600). EMJ saw most of the significant sound changes that took place in the language, as well as profound influence from Chinese, whereas most grammatical changes took place between the end of EMJ and the end of LMJ. By the end of LMJ, the Japanese language had reached a form that is not significantly different from present-day Japanese.
OJ phonology was simple, both in terms of phoneme inventory and syllable structure, with a total of only 88 different syllables. In EMJ, the language became quantity sensitive, with the introduction of a long versus short syllables. OJ and EMJ had obligatory verb inflection for a number of modal and syntactic categories (including an important distinction between a conclusive and an (ad)nominalizing form), whereas the expression of aspect and tense was optional. Through late EMJ and LMJ this system changed completely to one without nominalizing inflection, but obligatory inflection for tense.
The morphological pronominal system of OJ was lost in EMJ, which developed a range of lexical and lexically based terms of speaker and hearer reference. OJ had a two-way (speaker–nonspeaker) demonstrative system, which in EMJ was replaced by a three-way (proximal–mesial–distal) system.
OJ had a system of differential object marking, based on specificity, as well as a word order rule that placed accusative marked objects before most subjects; both of these features were lost in EMJ. OJ and EMJ had genitive subject marking in subordinate clauses and in focused, interrogative and exclamative main clauses, but no case marking of subjects in declarative, optative, or imperative main clauses and no nominative marker. Through LMJ genitive subject marking was gradually circumscribed and a nominative case particle was acquired which could mark subjects in all types of clauses.
OJ had a well-developed system of complex predicates, in which two verbs jointly formed the predicate of a single clause, which is the source of the LMJ and NJ (Modern Japanese) verb–verb compound complex predicates. OJ and EMJ also had mono-clausal focus constructions that functionally were similar to clefts in English; these constructions were lost in LMJ.
Reduplication is a word-formation process in which all or part of a word is repeated to convey some form of meaning. A wide range of patterns are found in terms of both the form and meaning expressed by reduplication, making it one of the most studied phenomenon in phonology and morphology. Because the form always varies, depending on the base to which it is attached, it raises many issues such as the nature of the repetition mechanism, how to represent reduplicative morphemes, and whether or not a unified approach can be proposed to account for the full range of patterns.
Erich R. Round
The non–Pama-Nyugan, Tangkic languages were spoken until recently in the southern Gulf of Carpentaria, Australia. The most extensively documented are Lardil, Kayardild, and Yukulta. Their phonology is notable for its opaque, word-final deletion rules and extensive word-internal sandhi processes. The morphology contains complex relationships between sets of forms and sets of functions, due in part to major historical refunctionalizations, which have converted case markers into markers of tense and complementization and verbal suffixes into case markers. Syntactic constituency is often marked by inflectional concord, resulting frequently in affix stacking. Yukulta in particular possesses a rich set of inflection-marking possibilities for core arguments, including detransitivized configurations and an inverse system. These relate in interesting ways historically to argument marking in Lardil and Kayardild. Subordinate clauses are marked for tense across most constituents other than the subject, and such tense marking is also found in main clauses in Lardil and Kayardild, which have lost the agreement and tense-marking second-position clitic of Yukulta. Under specific conditions of co-reference between matrix and subordinate arguments, and under certain discourse conditions, clauses may be marked, on all or almost all words, by complementization markers, in addition to inflection for case and tense.
Eystein Dahl and Antonio Fábregas
Zero or null morphology refers to morphological units that are devoid of phonological content. Whether such entities should be postulated is one of the most controversial issues in morphological theory, with disagreements in how the concept should be delimited, what would count as an instance of zero morphology inside a particular theory, and whether such objects should be allowed even as mere analytical instruments.
With respect to the first problem, given that zero morphology is a hypothesis that comes from certain analyses, delimiting what counts as a zero morpheme is not a trivial matter. The concept must be carefully differentiated from others that intuitively also involve situations where there is no overt morphological marking: cumulative morphology, phonological deletion, etc.
About the second issue, what counts as null can also depend on the specific theories where the proposal is made. In the strict sense, zero morphology involves a complete morphosyntactic representation that is associated to zero phonological content, but there are other notions of zero morphology that differ from the one discussed here, such as absolute absence of morphological expression, in addition to specific theory-internal interpretations of what counts as null. Thus, it is also important to consider the different ways in which something can be morphologically silent.
Finally, with respect to the third side of the debate, arguments are made for and against zero morphology, notably from the perspectives of falsifiability, acquisition, and psycholinguistics. Of particular impact is the question of which properties a theory should have in order to block the possibility that zero morphology exists, and conversely the properties that theories that accept zero morphology associate to null morphemes.
An important ingredient in this debate has to do with two empirical domains: zero derivation and paradigmatic uniformity. Ultimately, the plausibility that zero morphemes exist or not depends on the success at accounting for these two empirical patterns in a better way than theories that ban zero morphology.