In generative linguistics, Distributed Morphology is a theoretical framework introduced in 1993 by Morris Halle and Alec Marantz. The central claim of Distributed Morphology is that there is no divide between the construction of words and sentences. The syntax is the single generative engine that forms sound-meaning correspondences, both complex phrases and complex words. This approach challenges the traditional notion of the lexicon as the unit where derived words are formed and idiosyncratic word-meaning correspondences are stored. In Distributed Morphology there is no unified lexicon, as in earlier generative treatments of word-formation; rather, the functions that other theories ascribe to the lexicon are distributed among other components of the grammar.

Overview of Distributed Morphology

The basic principle of Distributed Morphology is that there is a single generative engine for the formation of both complex words and complex phrases: there is no division between syntax and morphology, and there is no lexicon—at least, not in the same sense as in traditional generative grammar. Any operation that would—according to lexicalist approaches—occur in the 'lexicon' is considered too vague in Distributed Morphology, which instead distributes these operations over various steps and lists.

The term 'Distributed Morphology' is used because the morphology of an utterance is the product of operations distributed over more than one step, with content from more than one list. In contrast to lexicalist models of morphosyntax, Distributed Morphology posits three components in building an utterance:

  1. The Formative List provides the input for syntax.
  2. The Exponent List (the list of vocabulary items) is consulted to provide the utterance with post-syntactic phonological content.
  3. Syntactic operations (such as Merge, Move or Agree, in the Minimalist framework) apply to formatives.

An additional list, the 'Encyclopedia', provides for the realization of non-compositional—idiomatic—meanings. Roots have no grammatical categories in and of themselves, and merely represent the bundle of semantic features to be exponed (see "Exponent list", below). The notation for roots in Distributed Morphology generally uses a square root symbol, with an arbitrary number or with the orthographic representation of the root. For example, love, without a grammatical category, could be expressed as √362 or as √LOVE.

Researchers adopting the Distributed Morphology approach agree that roots must be categorized by functional elements. There are multiple ways that this can be done. The following lists four possible routes.

  1. Roots are merged as modifiers to the functional elements that categorize them.
  2. Some roots are merged as modifiers and others as complements to the function elements that categorize them.
  3. Roots are inserted post-syntactically and do not merge with complements or modifiers.

As of 2020, there is no consensus on which approach most accurately describes the structural configuration of root categorization.

Exponent list: vocabulary items

Vocabulary items associate phonological content with arrays of underspecified syntactic and/or semantic features—the features listed in the lexicon—and they are the closest notion to the traditional morpheme concept as known from generative grammar. Postsyntactic Morphology posits that this operation takes place after the syntax itself has been expressed.

Vocabulary items are also known as the exponent list. In Distributed Morphology, after the syntax of a given utterance is complete, the exponent list must be consulted to provide phonological content. This is known as 'exponing' an item. In other words, a vocabulary item is a relation between a phonological string (which could also be zero or null) and the context in which this string may be inserted. Vocabulary items compete for insertion to syntactic nodes at spell-out, i.e. after syntactic operations are complete.

As an example of a vocabulary item, an affix in Russian can be exponed as follows:

<code>/n/ ←→ [___, +participant +speaker, plural]</code>

The phonological string on the left side is available for insertion to a node with the features described on the right side.

Roots, i.e. formatives from the formative list, are exponed based on their features. For example, the first-person singular pronominal paradigm in English is exponed as follows:

<code>[+1 +sing +nom +prn] ←→ /aj/

[+1 +sing +prn] ←→ /mi/</code>

The use of /mi/ does not seem infelicitous in a nominative context at first glance. If /mi/ acquired nominative case in the syntax, it would seem appropriate to use it. However, /aj/ is specified for the feature [+nom], and therefore must block the use of /mi/ in a nominative context. This is known as the Maximal Subset Condition or the Elsewhere Principle: if two items have a similar set of features, the one that is more specific will win. Illustrated in logical notation:

  • f(E1) ⊂ f(T), f(E2) ⊂ f(T), and f(E1) ⊂ f(E2) → f(E2) wins.

In this case, both /mi/ and /aj/ have a subset of features f(T), but /aj/ has the maximal subset.

Encyclopedia

The Encyclopedia associates syntactic units with special, non-compositional aspects of meaning. argue that Lowering applies before Vocabulary insertion, while Local Dislocation applies afterwards.

Apart from the operations described above, some researchers (Embick 1997 among others) have suggested that there are morphemes that represent purely formal features and are inserted post-syntactically but before spell-out: these morphemes are called "dissociated morphemes".

Morphological merger

Morphological Merger is generalized as follows in Marantz 1988: 261:

<blockquote>At any level of syntactic analysis (d-structure, s-structure, phonological structure), a relation between X and Y may be replaced by (expressed by) the affixation of the lexical head of X to the lexical head of Y.</blockquote>

Two syntactic nodes can undergo Morphological Merger subject to morphophonological well-formedness conditions.

An example can be found in Swahili, which has separate exponents for subject agreement (e.g., 1st plural tu-) and negation (ha-):

However, 1st person singular exponent ni- and negation ha- undergo fusion and realized as si-:

An alternative analysis of si- exponent says that there is no fusion but rather context sensitive allomorphy:

Fission

Fission refers to the splitting of one terminal node into two distinct terminal nodes prior to Vocabulary Insertion. Some of the most well-known cases of fission involve the imperfect conjugations of Semitic, in which agreement morphology is split into a prefixal and suffixal part, as investigated in the work of Noyer (1992). Fission may also occur where insertion of a Vocabulary item discharges the intrinsic features of the Vocabulary item from the terminal node, leaving others features available for possible insertion; if fission applies, then other Vocabulary items can be inserted to discharge the remaining features. When Fission occurs, the order of morphemes is influenced by the featural complexity of Vocabulary items.

Feature impoverishment

Impoverishment (a term introduced into the theory in Bonet 1991) refers to a change in the feature content on a terminal node prior to Vocabulary Insertion, resulting in a less marked feature content.

  • Feature deletion: This is accomplished by deleting a feature or by changing it from a marked to an unmarked value (e.g. [+plural] to [-plural]). Impoverishment accounts for cases in which spell-out of a terminal node by a featurally specific Vocabulary Item is blocked by a less specific Vocabulary Item.
  • Feature obliteration: Impoverishment can target an entire terminal node (rather than just one of its features), in which case it is referred to as 'obliteration'. This results in the complete absence of the morpheme from the structure of the word.

Lowering

Lowering is sensitive to syntactic headedness and operates on abstract feature bundles, after syntactic movement but prior to vocabulary insertion.

Containment hypothesis

The containment hypothesis is a theory under the framework of Distributed Morphology advanced by Bobaljik (2012) to account for the restrictions on the patterns of suppletion seen in language. It states:<blockquote>"The representation of the superlative properly contains that of the comparative (in all languages that have a morphological superlative)."