Modular design of grammar: Linguistics on the edge presents the cutting edge of research on linguistic modules and interfaces in Lexical-Functional Grammar (LFG). LFG has a highly modular design that models the linguistic system as a set of discreet submodules that include, among others, constituent structure, functional structure, argument structure, semantic structure, and prosodic structure, with each module having its coherent properties and being related to each other by correspondence functions. Following a detailed introduction, Part I scrutinises the nature of linguistic structures, interfaces and representations in LFG’s architecture and ontology. Parts II and III are concerned with problems, analyses and generalisations associated with linguistic phenomena which are of long-standing theoretical significance, including agreement, reciprocals, possessives, reflexives, raising, subjecthood, and relativisation, demonstrating how these phenomena can be naturally accounted for within LFG’s modular architecture. Part IV explores issues of the synchronic and diachronic dynamics of syntactic categories in grammar, such as unlike category coordination, fuzzy categorial edges, and consequences of decategorialization, providing explicit LFG solutions to such problems including those which result from language change in progress. The final part re-examines and refines the precise representations and interfaces of syntax with morphology, semantics and pragmatics to account for challenging facts such as suspended affixation, prosody in multiple question word interrogatives and information structure, anaphoric dependencies, and idioms.