It hasn’t come up much, but from “Spock Amok” back in season 1:

CHAPEL: No need. This is what I appreciate about Dever. He and I are on the same page. The casual, no attachments, this-is-just-for-fun, zero commitments page.

ORTEGAS: That’s more like a book than a page. And you said the same thing about that gal on Argelius II.

CHAPEL: That was a misunderstanding. It was one time.