Segment-level alternations that realize morphological properties or that have other morphological significance stand either at an interface or along a continuum between phonology and morphology. The typical source for morphologically correlated sound alternations is the automatic phonology, interacting with discrete morphological operations such as affixation. Traditional morphophonology depends on the association of an alternation with a distinct concatenative marker, but the rise of stem changes that are in themselves morphological markers, be they inflectional or derivational, resides in the fading of phonetic motivation in the conditioning environment, and thus an increase in independence from historical phonological sources. The clearest cases are sole-exponent alternations, such as English man~men or slide~slid, but it is not necessary that the remainder of an earlier conditioning affix be entirely absent, only that synchronic conditioning is fully opaque. Once a sound-structural pattern escapes the unexceptional workings of a language's general phonological patterning, yet reliably serves a signifying function for one or more morphological properties, the morphological component of the grammar bears a primary if not sole responsibility for accounting for the pattern’s distribution. It is not uncommon for the transition of analysis into morphology from (morpho)phonology to be a fitful one. There is an established tendency for phonological theory to hold sway in matters of sound generally, even at the expense of challenging learnability through the introduction of remote representations, ad hoc triggering devices, or putative rules of phonology of very limited generality. On the morphological side, a bias in favor of separable morpheme-like units and syntax-like concatenative dynamics has relegated relations like stem alternations to the margins, no matter how regular, productive, or distinct from general phonological patterns in the language in question overall. This parallel focus of each component on a "specialization" as it were has left exactly morphologically significant stem alternations such as Germanic Ablaut and Celtic initial-consonant mutation poorly served. In both families, these robust sound patterns generally lack reliable synchronic phonological conditioning. Instead, one must crucially refer to grammatical structure and morphological properties in order to account for their distributions. It is no coincidence that such stem alternations look phonological, just as fossils resemble the forms of the organisms that left them. The work of morphology likewise does not depend on alternant segments sharing aspects of sound, but the salience of the system may benefit from perceptible coherence of form. One may observe what sound relations exist between stem alternants, but it is neither necessary nor realistic to oblige a speaker/learner to generate established stem alternations anew from remote underlying representations, as if the alternations were always still arising; to do so constitutes a grafting of the technique of internal reconstruction as a recapitulating simulation within the synchronic grammar.
Thomas W. Stewart
Conjugation classes have been defined as the set of all forms of a verb that spell out all possible morphosyntactic categories of person, number, tense, aspect, mood, and/or other additional categories that the language expresses in verbs. Theme vowels instantiate conjugation classes as purely morphological markers; that is, they determine the verb’s morphophonological surface shape but not its syntactic or semantic properties. They typically split the vocabulary items of the category verb into groups that spellout morphosyntactic and morphosemantic feature specifications with the same inflectional affixes. The bond between verbs and their conjugational marking is idiosyncratic, and cannot be established on semantic, syntactic, or phonological grounds, although there have been serious attempts at finding a systematic correlation. The existence of theme vowels and arbitrary conjugation classes has been taken by lexicalist theories as empirical evidence to argue against syntactic approaches to word formation and are used as one of the main arguments for the autonomy of morphology. They further raise questions on the nature of basic morphological notions such as stems or paradigms and serve as a good empirical ground for theories of allomorphy and syncretism, or to test psycholinguistic and neurolinguistic theories of productivity, full decomposition, and storage. Conjugations and their instantiation via theme vowels may also be a challenge for theories of first language acquisition and the learning of morphological categories devoid of any semantic meaning or syntactic alignment that extend to second language acquisition as well. Thus, analyzing their nature, their representation, and their place in grammar is crucial as the approach to these units can have profound effects on linguistic theory and the architecture of grammar.
The morphological machinery of a language is at the service of syntax, but the service can be poor. A request may result in the wrong item (deponency), or in an item the syntax already has (syncretism), or in an abundance of choices (inflectional classes or morphological allomorphy). Network Morphology regulates the service by recreating the morphosyntactic space as a network of information sharing nodes, where sharing is through inheritance, and inheritance can be overridden to allow for the regular, irregular, and, crucially, the semiregular. The network expresses the system; the way the network can be accessed expresses possible deviations from the systematic. And so Network Morphology captures the semi-systematic nature of morphology. The key data used to illustrate Network Morphology are noun inflections in the West Slavonic language Lower Sorbian, which has three genders, a rich case system and three numbers. These data allow us to observe how Network Morphology handles inflectional allomorphy, syncretism, feature neutralization, and irregularity. Latin deponent verbs are used to illustrate a Network Morphology account of morphological mismatch, where morphosyntactic features used in the syntax are expressed by morphology regularly used for different features. The analysis points to a separation of syntax and morphology in the architecture of the grammar. An account is given of Russian nominal derivation which assumes such a separation, and is based on viewing derivational morphology as lexical relatedness. Areas of the framework receiving special focus include default inheritance, global and local inheritance, default inference, and orthogonal multiple inheritance. The various accounts presented are expressed in the lexical knowledge representation language DATR, due to Roger Evans and Gerald Gazdar.