How to phrase button labels?

1. What is a button label?
2. Should buttons be capitalized?

What is a button label?

Button labels inspire the users to take an action. To indicate what a button will do, use the function as the label of the button. When users read the button labels like Save, Preview, and Publish, they know exactly what the button will do when pressed.

Should buttons be capitalized?

Capitalize the first word of a sentence, heading, title, UI label (such as the name of a button or checkbox), or standalone phrase. Capitalize proper nouns. To learn more about proper nouns, see Nouns and pronouns. Use lowercase for everything else.