0 a verb that connects the qualities of an object or person to that object or person:
1 a verb that connects the subject of a sentence to the properties in the predicate:
The linking verb be is an obvious example.
The predicate can be an intransitive verb, a transitive verb followed by a direct object, a linking verb followed by a predicate nominative, etc.
The subject and predicative nominal must be connected by a linking verb, also called a copula.
The comparison is made by using the copula or linking verb is or its negative is not.
A subject complement (variously called a predicative expression, predicative, predicate noun or adjective, or complement) appears in a predicate with a linking verb (also called a copula).
While subject complements describe or modify the subject of a linking verb, object complements describe or modify nouns in the predicate, typically direct or indirect objects, or objects of adpositions.
Common linking verbs include "seem", "become", "appear", "look", and "remain".