believer noun

1 sb who has religious faith

ADJ. devout, genuine, true | religious

2 sb who believes that sth is good

ADJ. fervent, firm, great, passionate, staunch, strong

PREP. ~ in I'm a firm believer in the benefits of exercise.

believe verb

ADV. firmly, really, seriously (only used with negatives), sincerely He firmly believed that he was right. No one seriously believes that this war will happen. | mistakenly

VERB + BELIEVE can't/cannot, could not I couldn't believe what I was hearing. | be hard to It's hard to believe that this campaign has been going on for ten years. | give sb to The boss gave me to believe that we would all get a pay rise. | have reason to We have reason to believe that the escaped prisoner may be hiding in this house. | be inclined to I'm inclined to believe you. | lead sb to The advertisement led us to believe that all prices had been cut.

PHRASES can/could hardly/scarcely believe sth, not believe a word of sth I didn't believe a word of what he said.