In Modularity in Language, Etsuyo Yuasa investigates exceptions and idiosyncrasies in various complex clauses in Japanese and English within the framework of multi-modular approaches to grammar. She proposes original analyses of various complex clauses in Japanese and English, which deviate from the norms of other complex clauses in the same language or in other languages, and shows how these cases of syntax-semantics mismatch justify the independence (or 'autonomy') of different levels of grammatical structures.

Yuasa's significant contribution is the incorporation of the notion of 'construction' from Construction Grammar into multi-modular approaches to grammar. She claims that the idiosyncratic cases examined in this study are instances of constructional and categorial mismatches where a syntactic representation of a prototypical construction is paired with a semantic representation of another prototypical construction.

Modularity in Language is aimed at those interested in grammatical theories in general, the parallel architecture of grammar (including Lexical-Functional Grammar, Autolexical Grammar, Representational Modularity), Constructional Grammar, syntax/semantics interface, and Japanese linguistics.