Cognitive grammar is a cognitive approach to language developed by Ronald Langacker, which considers the basic units of language to be symbols or conventional pairings of a semantic structure with a phonological label. Grammar consists of constraints on how these units can be combined to generate larger phrases which are also a pairing of semantics and phonology. The semantic aspects are modeled as image schemas rather than propositions, and because of the tight binding with the label, each can invoke the other.Cognitive Grammar belongs to the wider movement known as cognitive linguistics, which in turn is part of the functional tradition. Besides cognitive grammar, important strands of cognitive linguistics include construction grammar, metaphor theory, the study of blends and mental spaces, and various efforts to develop a conceptualist semantics. Among other major components of functionalism are discourse-pragmatic analyses, the study of grammaticalization, and universal-typological investigation via crosslinguistic surveys. Naturally, terms like "cognitive linguistics" and "functionalism" are fluid in reference and subsume a diverse array of views. There is at best a broad compatibility of outlook among the scholars concerned, certainly not theoretical uniformity.