一定 yīdìng HSK2 certainly Origin Definitions Defs Strokes Stroke Words Sentences Sents 不一定 bùyīdìng not necessarily not necessarily; used to express that something is not certain to happen or be true一定之规 yīdìngzhīguī fixed rule a fixed pattern or set rule; a set idea that is hard to change一定要 yīdìngyào must must; definitely have to; to be determined to