believe in

verb

believed in; believing in; believes in

1

: to have faith or confidence in the existence of (something)

Do you believe in ghosts?

2

: to have trust in the goodness or value of (something)

She believes in (the value of) regular exercise.

I believe in working hard to achieve success.

She doesn't believe in using pesticides.

3

: to have trust in the goodness or ability of (someone)

Despite his problems, his parents still believe in him.