so related that each implies or complements the other.

being in correlation; mutually related.

Grammar . answering to or complementing one another and regularly used in association, as either and or, not only and but.

Biology . (of a typical structure of an organism) found in correlation with another.

either of two things, as two terms, that are correlative.

Grammar . a correlative expression.

noun

analogue , congener , correlate , correspondent , counterpart , match