How is stop used as noun?

A noun functions as the subject of a sentence or a clause, and as the object of a verb or a preposition.

Examples:

The stop at thirty-fourth street is nearest to my office. (subject of the sentence)

We made a stop for fuel at the halfway point. (direct object of the verb 'made')

I came to a complete stop. (object of the preposition 'to')

The Word 'stop' is also a verb and an adjective.