believe in somebody/something phrasal verb ( see also ↑ believe )
1 . to be sure that someone or something exists:
Do you believe in God?
2 . to think that something is effective or right:
I don’t believe in these diets.
believe in doing something
The school believes in letting children learn at their own pace.
3 . to trust someone and be confident that they will be successful:
The people want a president they can believe in.
Believe in yourself, or you’ll never succeed.