believe in something—
1. have trust in smth.; feel sure of the value of smth.:
- The United States believes in the great potential of Africa.
2. feel sure of the existence of smth.:
- Clever farmers made good use of the belief of these people who believed in ghosts.
believe something—feel sure of the truth of smth.:
- I want to believe this story, but then again I still have a lot of doubts about its authenticity.