CREDIBLE/CREDULOUS

"Credible” means “believable” or “trustworthy.” It is also used in a more abstract sense, meaning something like “worthy”: “She made a credible lyric soprano.” Don’t confuse “credible” with “credulous,” a much rarer word which means “gullible.” “He was incredulous” means “he didn’t believe it” whereas “he was incredible” means “he was wonderful” (but use the latter expression only in casual speech).