believe in

1. 1.

   have a firm conviction as to the goodness of something

   “John believes in oat bran”

   Broaderbelieve

Questions about believe in

What does believe in mean?

believe in means "have a firm conviction as to the goodness of something".

Is believe in a common word?

believe in is banded "Familiar" — widely understood, used when the subject calls for it. The band comes from how often the word appears in a large corpus of everyday English, not from an editor's impression.