credible
adjective
able to be believed; convincing:
〈話･証拠などが〉信用［信頼］できる; 確実な
e.g. few people found his story credible
e.g. a credible witness.
capable of persuading people that something will happen or be successful:
〈方法･人などが〉(成功などの)見込みのある, 可能性のある(↔ incredible)
e.g. a credible threat.
ORIGIN
late Middle English: from Latin credibilis, from credere ‘believe’.