Noun:
* A theatrical performance: "We went to see a new play at the theater."
* A piece of writing intended for theatrical performance: "Shakespeare's plays are still performed today."
* A game or activity: "Children love to play games."
Verb:
* To engage in a game or activity: "The kids are playing in the backyard."
* To perform in a play: "She plays the role of Juliet."
* To perform music: "The band played a beautiful melody."
To understand the correct usage, you need to look at the sentence as a whole.