Here are some examples:
* They play in the park. (Verb in present tense)
* I played the piano. (Verb in past tense)
* Let's play a game. (Verb in imperative mood)
However, "play" can also be a noun. For example:
* He's a good play writer.
* The play was a success.
To determine whether "play" is a verb or a noun in a sentence, you need to look at the context.