Copular sentences (sentences of the form A is B) have been prominent on the research agenda for linguists and philosophers of language since classical antiquity, and continue to be shrouded in considerable controversy. Central questions in the linguistic literature on copulas and copular sentences are (a) whether predicational, specificational, identificational, and equative copular sentences have a common underlying source; and, if so, (b) how the various surface types of copular sentences are derived from that underlier; (c) whether there is a typology of copulas; and (d) whether copulas are meaningful or meaningless. The debate surrounding the postulation of multiple copular sentence types relies on criteria related to both meaning and form. Analyses based on meaning tend to focus on the question of whether or not one of the terms is a predicate of the other, whether or not the copula contributes meaning, and the information-structural properties of the construction. Analyses based on form focus on the flexibility of the linear ordering of the two terms of the construction, the surface distribution of the copular element, the restrictions imposed on the extraction of the two terms, the case and agreement properties of the construction, the omissibility of the copula or one of the two terms, and the connectivity effects exhibited by the construction. Morphosyntactic variation in the domain of copular elements is an area of research with fruitful intersections between typological and generative approaches. A variety of criteria are presented in the literature to justify the postulation of multiple copulas or underlying representations for copular sentences. Another prolific body of research concerns the semantics of copular sentences. In the assessment of scholarship on copulas and copular sentences, the article critiques the ‘multiple copulas’ approach and examines ways in which the surface variety of copular sentence types can be accounted for in a ‘single copula’ analysis. The analysis of copular constructions continues to have far-reaching consequences in the context of linguistic theory construction, particularly the question of how a predicate combines with its subject in syntactic structure.