Bracketing paradoxes—constructions whose morphosyntactic and morpho-phonological structures appear to be irreconcilably at odds (e.g., unhappier)—are unanimously taken to point to truths about the derivational system that we have not yet grasped. Consider that the prefix un- must be structurally separate in some way from happier both for its own reasons (its [n] surprisingly does not assimilate in Place to a following consonant (e.g., u[n]popular)), and for reasons external to the prefix (the suffix -er must be insensitive to the presence of un-, as the comparative cannot attach to bases of three syllables or longer (e.g., *intelligenter)). But, un- must simultaneously be present in the derivation before -er is merged, so that unhappier can have the proper semantic reading (‘more unhappy’, and not ‘not happier’). Bracketing paradoxes emerged as a problem for generative accounts of both morphosyntax and morphophonology only in the 1970s. With the rise of restrictions on and technology used to describe and represent the behavior of affixes (e.g., the Affix-Ordering Generalization, Lexical Phonology and Morphology, the Prosodic Hierarchy), morphosyntacticians and phonologists were confronted with this type of inconsistent derivation in many unrelated languages.
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.
Due to the agglutinative character, Japanese and Ryukyuan morphology is predominantly concatenative, applying to garden-variety word formation processes such as compounding, prefixation, suffixation, and inflection, though nonconcatenative morphology like clipping, blending, and reduplication is also available and sometimes interacts with concatenative word formation. The formal simplicity of the principal morphological devices is counterbalanced by their complex interaction with syntax and semantics as well as by the intricate interactions of four lexical strata (native, Sino-Japanese, foreign, and mimetic) with particular morphological processes. A wealth of phenomena is adduced that pertain to central issues in theories of morphology, such as the demarcation between words and phrases; the feasibility of the lexical integrity principle; the controversy over lexicalism and syntacticism; the distinction of morpheme-based and word-based morphology; the effects of the stage-level vs. individual-level distinction on the applicability of morphological rules; the interface of morphology, syntax, and semantics, and pragmatics; and the role of conjugation and inflection in predicate agglutination. In particular, the formation of compound and complex verbs/adjectives takes place in both lexical and syntactic structures, and the compound and complex predicates thus formed are further followed in syntax by suffixal predicates representing grammatical categories like causative, passive, negation, and politeness as well as inflections of tense and mood to form a long chain of predicate complexes. In addition, an array of morphological objects—bound root, word, clitic, nonindependent word or fuzoku-go, and (for Japanese) word plus—participate productively in word formation. The close association of morphology and syntax in Japonic languages thus demonstrates that morphological processes are spread over lexical and syntactic structures, whereas words are equipped with the distinct property of morphological integrity, which distinguishes them from syntactic phrases.
Tone is indispensable for understanding many morphological systems of the world. Tonal phenomena may serve the morphological needs of a language in a variety of ways: segmental affixes may be specified for tone just like roots are; affixes may have purely tonal exponents that associate to segmental material provided by other morphemes; affixes may consist of tonal melodies, or “templates”; and tonal processes may apply in a way that is sensitive to morphosyntactic boundaries, delineating word-internal structure. Two behaviors set tonal morphemes apart from other kinds of affixes: their mobility and their ability to apply phrasally (i.e., beyond the limits of the word). Both floating tones and tonal templates can apply to words that are either phonologically grouped with the word containing the tonal morpheme or syntactically dependent on it. Problems generally associated with featural morphology are even more acute in regard to tonal morphology because of the vast diversity of tonal phenomena and the versatility with which the human language faculty puts pitch to use. The ambiguity associated with assigning a proper role to tone in a given morphological system necessitates placing further constraints on our theory of grammar. Perhaps more than any other morphological phenomena, grammatical tone exposes an inadequacy in our understanding both of the relationship between phonological and morphological modules of grammar and of the way that phonology may reference morphological information.
Subtraction consists in shortening the shape of the word. It operates on morphological bases such as roots, stems, and words in word-formation and inflection. Cognitively, subtraction is the opposite of affixation, since the latter adds meaning and form (an overt affix) to roots, stems, or words, while the former adds meaning through subtraction of form. As subtraction and affixation work at the same level of grammar (morphology), they sometimes compete for the expression of the same semantics in the same language, for example, the pattern ‘science—scientist’ in German has derivations such as Physik ‘physics’—Physik-er ‘physicist’ and Astronom-ie ‘astronomy’—Astronom ‘astronomer’. Subtraction can delete phonemes and morphemes. In case of phoneme deletion, it is usually the final phoneme of a morphological base that is deleted and sometimes that phoneme can coincide with a morpheme. Some analyses of subtraction(-like shortenings) rely not on morphological units (roots, stems, morphological words, affixes) but on the phonological word, which sometimes results in alternative definitions of subtraction. Additionally, syntax-based theories of morphology that do not recognize a morphological component of grammar and operate only with additive syntactic rules claim that subtraction actually consists in addition of defective phonological material that causes adjustments in phonology and leads to deletion of form on the surface. Other scholars postulate subtraction only if the deleted material does not coincide with an existing morpheme elsewhere in the language and if it does, they call the change backformation. There is also some controversy regarding what is a proper word-formation process and whether what is derived by subtraction is true word-formation or just marginal or extragrammatical morphology; that is, the question is whether shortenings such as hypocoristics and clippings should be treated on par with derivations such as, for example, the pattern of science-scientist. Finally, research in subtraction also faces terminology issues in the sense that in the literature different labels have been used to refer to subtraction(-like) formations: minus feature, minus formation, disfixation, subtractive morph, (subtractive) truncation, backformation, or just shortening.