Compound and complex predicates—predicates that consist of two or more lexical items and function as the predicate of a single sentence—present an important class of linguistic objects that pertain to an enormously wide range of issues in the interactions of morphology, phonology, syntax, and semantics. Japanese makes extensive use of compounding to expand a single verb into a complex one. These compounding processes range over multiple modules of the grammatical system, thus straddling the borders between morphology, syntax, phonology, and semantics. In terms of degree of phonological integration, two types of compound predicates can be distinguished. In the first type, called tight compound predicates, two elements from the native lexical stratum are tightly fused and inflect as a whole for tense. In this group, Verb-Verb compound verbs such as arai-nagasu [wash-let.flow] ‘to wash away’ and hare-agaru [sky.be.clear-go.up] ‘for the sky to clear up entirely’ are preponderant in numbers and productivity over Noun-Verb compound verbs such as tema-doru [time-take] ‘to take a lot of time (to finish).’
The second type, called loose compound predicates, takes the form of “Noun + Predicate (Verbal Noun [VN] or Adjectival Noun [AN]),” as in post-syntactic compounds like [sinsya : koonyuu] no okyakusama ([new.car : purchase] GEN customers) ‘customer(s) who purchase(d) a new car,’ where the symbol “:” stands for a short phonological break. Remarkably, loose compounding allows combinations of a transitive VN with its agent subject (external argument), as in [Supirubaagu : seisaku] no eiga ([Spielberg : produce] GEN film) ‘a film/films that Spielberg produces/produced’—a pattern that is illegitimate in tight compounds and has in fact been considered universally impossible in the world’s languages in verbal compounding and noun incorporation.
In addition to a huge variety of tight and loose compound predicates, Japanese has an additional class of syntactic constructions that as a whole function as complex predicates. Typical examples are the light verb construction, where a clause headed by a VN is followed by the light verb suru ‘do,’ as in Tomodati wa sinsya o koonyuu (sae) sita [friend TOP new.car ACC purchase (even) did] ‘My friend (even) bought a new car’ and the human physical attribute construction, as in Sensei wa aoi me o site-iru [teacher TOP blue eye ACC do-ing] ‘My teacher has blue eyes.’ In these constructions, the nominal phrases immediately preceding the verb suru are semantically characterized as indefinite and non-referential and reject syntactic operations such as movement and deletion. The semantic indefiniteness and syntactic immobility of the NPs involved are also observed with a construction composed of a human subject and the verb aru ‘be,’ as Gakkai ni wa oozei no sankasya ga atta ‘There was a large number of participants at the conference.’ The constellation of such “word-like” properties shared by these compound and complex predicates poses challenging problems for current theories of morphology-syntax-semantics interactions with regard to such topics as lexical integrity, morphological compounding, syntactic incorporation, semantic incorporation, pseudo-incorporation, and indefinite/non-referential NPs.