Linking verbs (be, seem, appear, become, taste, smell, feel, look, sound) connect the subject to a subject complement, which is a word or phrase that renames or describes the subject. The subject complement can be a noun (Mary is a teacher), an adjective (The soup tastes salty), or a noun phrase (She became the team captain). Unlike action verbs, linking verbs do not show action; instead, they show a state of being or a change in state.
You already know that copular and linking verbs work differently from action verbs — they do not express something the subject *does* but rather something the subject *is* or *becomes*. This topic builds that understanding into a precise account of the sentence structure linking verbs create. When a linking verb appears, what follows it is not an object (a thing acted upon) but a subject complement — a word or phrase that loops back and refers to the subject itself, either renaming it or describing it.
The two types of subject complement operate differently. A predicate nominative (also called a predicate noun) renames the subject as a different noun: *Mary is a teacher* — "a teacher" renames "Mary." A predicate adjective describes a quality the subject has: *The soup tastes salty* — "salty" describes "the soup." The linking verb in both cases acts as an equals sign, connecting subject to complement without absorbing either into its own action.
This structure creates a subtle agreement challenge that trips up careful writers: when the subject and predicate nominative differ in number, the verb agrees with the subject, not the complement. *The biggest problem is the long delays.* "Problem" is singular and governs the verb, even though "delays" (plural) comes right before the end. Native speakers sometimes hear the plural noun and incorrectly shift to *are*, but grammatically, the verb always tracks the subject that precedes it. Testing whether a verb is linking (rather than action) is the first diagnostic step: can you substitute a form of *be* without changing the basic meaning? *The soup tastes salty* → *The soup is salty*. If yes, it is a linking verb, and the word following it is a complement, not an object.
Not all uses of these verbs are linking uses. *She felt the fabric* is an action sentence — "the fabric" is an object being touched, not a complement describing "she." *She felt tired* is linking — "tired" describes her state. The distinction matters because only the linking use creates a complement, and only complements participate in the agreement and case patterns described here. Learning to identify linking versus action usage in context is the transferable skill this topic develops — it applies across all the verbs in the linking-verb family, not just *be*.