Google Material Writing

As you'd expect from Google, the Material writing guide focuses on writing superb interface copy, with a fairly standard emphasis on clarity, concision, accessibility, and direct address. Note that Google calls out the basis for their style guide, the Associated Press, which is a smart way to cover topics you don't intend to include in your own guide.

From the guide

Text should be simple, concise, and direct

Text should be understandable by anyone, anywhere, regardless of their culture or language.

Clear, accurate, and concise text makes interfaces more usable and builds trust.

In addition to these guidelines, be sure to consult guidelines for specific UI elements, such as ErrorsDialogsSettings, and Data formats.

Style

Google guidelines generally follow the Associated Press (AP) style guidelines.

Read the rest of the Material writing guide