A finite verb is a verb that has a grammatical tense and that can stand alone as the verb of a sentence. Every sentence must include a finite verb, whether a transitive, intransitive, or linking verb. In English, finite verbs typically end in "s" or "ed," or are uninflected — meaning they do not have a suffix. The identifying trait of a finite verb in any language is that it always has a tense, and is therefore finite, or limited, by time.
A finite verb may also be a verb phrase, which contains one or more helping or axillary verbs plus a main verb, as in "The girls were hula-hooping," where "were hula-hooping" is the finite verb. In some languages, this construction is considered a linking verb with a participle, but English grammars typically classify the whole phrase as the finite verb.
In contrast to finite verbs, which never have any role except that of a verb, non-finite verbs, often called "verbals," function as nouns or adjectives. The three types of non-finite verbs are gerunds, infinitives and participles. Gerunds are verbs that function as nouns, ending in "ing" in English. Infinitives are verb phrases that begin with "to," as in, "to munch." Participles are verbs that function as adjectives, usually ending in "ed," "en," or "ing" in English.
To determine whether an "ed" verb is finite, one should look at its role in the sentence. It is often easier to discover a finite verb by process of elimination; if it is not one of the three non-finite forms, it is finite. In the sentence, "Pedro baked a chicken for dinner," "baked" is not used as a noun, it is not preceded by "to," and it is not used as an adjective; therefore, it is finite.
Some confusion may arise from verb forms ending in "ed," which might be either finite or non-finite. Again, its role in the sentence must be considered. For instance, "Pedro ate baked chicken for dinner" contains the same word form, "baked," as the preceding example. In this sentence the word "baked" is a participle because it functions as a adjective describing what kind of chicken Pedro ate, so it is non-finite.
Another way to think of finite verbs is that they change their form based on the grammatical number and person of the sentence's subject as well as on the tense of the verb. For example, the verb "steer" has different forms depending on who is steering and when: "I steer," has no inflection, while "He steers" ends in "s," and "We steered" ends in "ed." The three types of non-finite verbs, however, do not change their form based on other words in the sentence.
In standard English grammar, a sentence must contain at least one finite verb, but it may contain many or no non-finite verbs. The sentence "Jane wanted to splash in the wading pool" contains one finite verb, "wanted," and two non-finite verbs, "to splash" and "wading."