behaving in a way that is not sensible and is typical of people who are much younger （行为）不成熟的，不够老练的，幼稚的 immature behaviour 不成熟的行为
Extra ExamplesTopics Personal qualitiesb2, Life stagesb2Although she was older than her husband, she was emotionally quite immature. 尽管她比丈夫大，在情绪方面却不很成熟。 He displays very immature behaviour for a boy of 16, running about the classroom and yelling. 作为一个16岁的男孩，他表现出非常不成熟的行为，在教室里跑来跑去，大喊大叫。 Oh, don't be so immature. 哦，别这么幼稚。
Oxford Collocations Dictionaryverbs- be
- seem
- sound
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- extremely
- fairly
- very
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not fully developed or grown 未长成的；发育未全的 immature plants 未长成的植物 The immature birds have shorter tails and brown, speckled plumage. 发育未全的鸟尾巴较短，羽毛呈褐色，有斑点。
Oxford Collocations Dictionaryverbs- be
- seem
- sound
- …
- extremely
- fairly
- very
- …
opposite mature
Word Originmid 16th cent. (in the sense ‘premature’, referring to death): from Latin immaturus ‘untimely, unripe’, from in- ‘not’ + maturus ‘ripe’.