believe in

Calque of the Latin use of crēdō (“believe”) with in plus accusative.

believe in (third-person singular simple present believes in, present participle believing in, simple past and past participle believed in)

1. (transitive) To ascribe existence to.

   Do you believe in God? / the Easter Bunny? / ghosts?

   Since I don't believe in reincarnation, I believe that the only way to eliminate suffering is to die.

2. (transitive) To believe that (something) is right or desirable.

   I don't believe in sex before marriage.

   I don't believe in making my bed.

   • 2017 June 23, "Is spokes model Cindy Margolis married or single after her divorce with Guy Starkman, Know her current affairs", Hitberry.com

     The couple is one of the celebrities who believed in open relationships.

3. (transitive) To have confidence in the ability or power of.

   I believe in you, man! You can do it!