know, learn, comprehend, understand 这些动词都含"懂，知道，明了"之意。
know: 普通用词，多指通过学习、经验或他人传播而得到知识，含直接知道的意味。
【英释】If you know a fact, a piece of information, or an answer, you have it correctly in your mind.
【例句】 I don't know the name of the place.
我不知道那个地方的名字。
learn: 通常指通过他人而获得消息或情况，侧重从不知到知的变化过程。
【英释】If you learn of something, you find out about it.
【例句】 It was only after his death that she learned of his affair with Betty.
一直到他死后她才知道他和贝蒂有染。
comprehend : 侧重熟悉了解的过程。
【英释】If you cannot comprehend something, you cannot understand it.
【例句】 I just cannot comprehend your attitude.
我就是无法理解你的态度。
understand : 指对事物已有彻底的认识，不仅知其性质、含义和细节，而且了解其内外的关系。
【英释】You say that you understand something when you know why or how it happens.
【例句】They are too young to understand what is going on.
他们还太小，不明白发生了什么事。
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