In a sentence, the subject does something. The verb tells the action of the subject.
John rides.
The baby cries.
The wind blows.
Sarah reads.
Some sentences have only a verb. In those sentences, the subject is understood to be the word you.
Stop!
Listen up!
Wait!
These command sentences use only a verb, but the subject is understood to be the person spoken to.
Use a verb in every sentence that you write. In a command sentence, there is no written subject.
▶It’s your turn. Find the verb in this sentence. The man rang the doorbell. Did you find the action? Good for you!