心虚:1someone did something wrong or bad, but afraid of being found out and with a guilty conscience.例如:他摔坏了爸爸的眼镜却不敢说，所以一见到爸爸他就感觉很心虚。 2 lack of self-confidence.例如:他刚接手这项工作，有点心虚。 虚心: open-minded or modest.例如:学习需要虚心请教，才可取得进步。

发展中国家虚心向世界学习技术，但某些发达国家有些心虚不愿合作。

虚心做某事就是你用一种谦卑的态度去做某事 心虚是因为做了某种bad thing而不敢或者不好意思去做另一件事

It might be difficult for foreigners to differentiate word combinations, even native speakers are. 心虛 is a VH, an intransitive state verb. Specifically, it is a subject(心)-predicate(虛) construction. When your heart feels rather empty, you feel diffident. There is a similar phrase 膽/dan3/: gut 虛. When a man is not with plenty of guts, he is timid or frightened. Though 虛心 is a VH, it's a verb(虛 to reserve)-obj(心) construction. When you reserve your heart, you won't be occupated with bias. There is a similar construction 虛左, describing to reserve an honored post for someone competent.

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