cop·u·la 
(kŏpyə-lə)
(kŏpyə-lə)n.
1. A verb, such as a form of be or seem, that identifies the predicate of a sentence with the subject. Also called linking verb.
2. Logic The word or set of words that serves as a link between the subject and predicate of a proposition.
[Latin cōpula, link.]
copu·lar (-lər) adj.