Functional Grammar is a model of grammar motivated by functions. The model was originally developed by Simon C. Dik at the University of Amsterdam in the 1970s, and has undergone several revisions ever since. The latest standard version under the original name is laid out in the two-volume 1997 edition1, published shortly after Dik's tragic death of cancer. The latest incarnation features the expansion of the model with a pragmatic/interpersonal module by Kees Hengeveld and Lachlan Mackenzie2. This has led to a renaming of the theory to "Functional Discourse Grammar". This type of grammar is quite distinct from systemic functional grammar as developed by Michael Halliday and many other linguists since the 1970s.
Semantic function (Agent, Patient, Recipient, etc.), describing the role of participants in states of affairs or actions expressed
Syntactic functions (Subject and Object), defining different perspectives in the presentation of a linguistic expression
Pragmatic functions (Theme and Tail, Topic and Focus), defining the informational status of constituents, determined by the pragmatic context of the verbal interaction
Dik, SC, The Theory of Functional Grammar (Part I: The Structure of the clause), 1989
Hurford, J. (1990) Nativist and functional explanations in language acquisition. In I. M. Roca (ed.), Logical Issues in Language Acquisition, 85-136. Foris, Dordrecht.