Functional theories of grammar refer to linguistic theories that attempt to explain the structure of language in terms of its function in communication. Synonyms for this term include functional grammar, communicative grammar, and discourse-functional grammar. These approaches differ from formal grammar, which focuses on grammatical structures and rules, by emphasizing that language use is primarily communicative and that grammar should be studied in context. Other related terms include usage-based grammar, which emphasizes the importance of language use in shaping grammar, and cognitive grammar, which considers the role of cognition in grammar. These various theories have contributed to a better understanding of how language structure and use are linked, and how they can vary across different languages and contexts.