In linguistics, a copula is a word used to link the subject of a sentence with a predicate, such as the word is in the sentence “The sky is blue. ” 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.