不一定
bù​yī​dìng HSK2

not necessarily

bù​yī​dìng not necessarily
  1. 不 bù adverb
    not
    Negative adverb used before verbs, adjectives, and other adverbs to indicate negation; also used as a bound-form prefix to form terms with opposite meanings
  2. 一定 yī​dìng adverb
    certainly
    certainly; surely; definitely; used to express a strong intention or a firm conclusion

bù​yī​dìng uncertain
  1. 不 bù adverb
    not
    Negative adverb used before verbs, adjectives, and other adverbs to indicate negation; also used as a bound-form prefix to form terms with opposite meanings
  2. 一定 yī​dìng determiner
    fixed
    fixed; specified; definite; regular; having a set or unchangeable nature