Identify the verb in the sentence: "The cat sleeps on the couch."

In the sentence "The cat sleeps on the couch," the verb is "sleeps." Verbs are action words that describe what the subject is doing. In this case, the subject is "the cat," and the action it is performing is sleeping. "Sleeps" clearly indicates the activity that the cat is engaged in.

The other words in the sentence serve different grammatical functions: "the" is a definite article modifying the noun "cat," "cat" is the subject of the sentence, and "on" is a preposition that shows the relationship between "sleeps" and "the couch." Each of these plays an important role in forming the sentence, but only "sleeps" indicates the action being taken by the subject.