Functional Grammar

Functional grammar is the general theory of the organization of natural language. FG wishes to be a theory whis is "functional" in at least three different, though interreleted senses:

• it takes a functional view on the nature of language
• it attaches primary importance to functional relations at different levels in the organization of grammar
• it wishes to be practically applicable to the analysis of different aspects of language and language use.

Lexical functional grammar is a theory of grammar that is, in general terms, a theory of:

• Syntax (roughly, how words can be combined together to make larger phrases, such as sentences) define different prespectives though which states of affairs are presented in linguistic expressions.
• Morphology (how morphemes - parts of words, such as the  parts of writers, namely the verb write, the "agentive affixes" -er and the plural markes -s -can be combined to make up words)
• Semantics (how and why various words and combinations of words mean what they mean) define roles that participants play in states of affairs, as designated by predications.

In addition, grammar is often taken to include phonology (the study of the sound systems of human languages), but LFG has relatively little to say about this.
In LFG, there are 2 parallel levels of syntactic representation: constituent structure (c-structure) and functional structure (f-structure)

• C-structures have the form of context-free phrase structure trees.
• F-structure are seen of pairs of attributes and values: attributes may be features, such as tense and gender, or functions, such as subject and object.

the names of theory emphasizes an important difference between LFG and the Chomsky tradition from which it developed: many phenomena are though to be more naturally analysed in terms of grammatical functions as represented in the lexicon or in F-structure, rather than on the level of phrase structure. An example is the alternation between active and passive, which rather than beign treated as transformation, is handled in the lexicon. Grammatical functions are not derived from the phrase structure configurations, but are represented at the parallel level of functional structure.