In linguistics, a copula (plural: copulas or copulae; abbreviated cop) is a word or phrase that links the subject of a sentence to a subject complement, such as the word is in the sentence "The sky is blue" or the phrase was not being in the sentence "It was not being used." The word copula derives from the Latin noun for a "link" or "tie" that connects two different things.
A copula is often a verb or a verb-like word, though this is not universally the case. A verb that is a copula is sometimes called a copulative or copular verb. In English primary education grammar courses, a copula is often called a linking verb. In other languages, copulas show more resemblances to pronouns, as in Classical Chinese and Guarani, or may take the form of suffixes attached to a noun, as in Korean, Beja, and Inuit languages.
Most languages have one main copula, although some (like Spanish, Portuguese and Thai) have more than one, and some have none. In the case of English, this is the verb to be. While the term copula is generally used to refer to such principal forms, it may also be used to refer to some other verbs with similar functions, like become, get, feel and seem in English; these may also be called "semi-copulas" or "pseudo-copulas".