Lexical-Functional Grammar (LFG) is a theoretical framework in linguistics that focuses on the relationship between syntax and semantics. It posits that sentences have two levels of structure: the constituent structure, which represents how words combine to form phrases and sentences, and the functional structure, which captures grammatical relations like subject and object. LFG emphasizes the importance of the lexicon, where words carry both meaning and grammatical information. This approach allows for a flexible understanding of language, accommodating various syntactic phenomena across different languages while maintaining a clear distinction between form and function in sentence construction.