In grammar, conjoins are elements<!-- not sure if "element" is the right term --> that are connected by a coordinating conjunction. In other words, conjoins are what undergo coordination, so this could be a coordinated clause or phrase or one word, e.g. 'by hook' or 'by crook,' 'boys' and 'girls,' 'red,' and 'blue.' "Conjoin" can also be a verb, which simply means to join 2 equal units together.

In mathematics and logic, conjoin refers to the operation of combinating two sets, conditions, or expressions by a logical AND. Conjoining two sets, for example, produces a set of only those elements which are in both sets. Conjoining two conditions, for example, requires that both conditions apply. The term intersection is more commonly used in set theory. For contrast, the union operation, is the logical OR. The union of two sets includes every element in either set, and the union of two conditions requires only that either (or both) be true.

External link

Conjoin @ The Internet Grammar of English