Cognitive Grammar (CG), previously known as “space grammar,” is a theory of language within the cognitive linguistics camp developed by Ronald Langacker from the late 1970s onward. Its development can be divided into two stages: “classical” CG—from its inception to the turn of the twenty-first century—and contemporary CG. Classical CG aims to offer an alternative to formal/generative grammar by rejecting the view of grammar as an autonomous module of an autonomous language faculty and, consequently, by espousing the view that language should be treated as part of general cognition. Thus, CG rejects the mainstream generative assumption that language consists of a repository of forms (the lexicon of a language) and a set of rules for combining them (the syntax of a language). Instead, lexicon and syntax are seen as two facets of a grammar-lexicon continuum and language is viewed as a “structured inventory of conventional units.” This means that a language consists of linguistic expressions of any length and specificity that are entrenched in the language user’s mind (they are units), are shared among the speakers of the language (they are conventional), and are related to one other by various types of links (they are a “structured” inventory). Importantly, linguistic units emerge out of specific usage events, so CG is described as a usage-based model of language. Also, all linguistic expressions, of any length and specificity, are regarded as symbolic in the sense that they are made up by a semantic pole (the “meaning” of an expression), a phonological pole (the “form” of an expression), as well as their linking. Unlike in other more mainstream approaches, these two poles are construed broadly so that the semantic pole encompasses pragmatic/encyclopedic information and the phonological pole includes bodily manifestations other than speech, such as gesture. A corollary of the symbolic view is that “grammar” is inherently meaningful, as grammatical patterns also consist in the association of a semantic pole and a phonological pole, no matter how abstract they might be. Contemporary CG focuses on offering a unified treatment of language structure, processing, and discourse. One of the key claims is that traditional hierarchical constituency, as represented in syntactic trees, is problematic because grammatical structure is actually often serial or flat. CG has many affinities to Goldberg’s Construction Grammar (CxG) and Croft’s Radical Construction Grammar (RCC), although it is much broader in scope and important differences exist. For example, CxG and RCC also describe linguistic expressions as pairings of form and meaning, but CxG and RCC equate form with syntax while CG equates form with phonology. Instead, syntax, as pointed out earlier, has no independent status in CG.