know、learn、comprehend与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。
- She knows the name of every kid in the school.
她知道学校里每个孩子的名字。 - I don't know anything about this.
我对此一无所知。 - Even small amounts of these substances are known to cause skin problems.
我们知道这类物质即使是一丁点也会损害皮肤。 - The authorities know him to be (= know that he is) a cocaine dealer.
当局知道他是个可卡因贩子。
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。
- We were all shocked to learn of his death.
听到他的死讯我们都很震惊。 - I later learned (that) the message had never arrived.
我后来听说从来就没有收到过那条消息。 - I only learned about the accident later.
那起事故我只是后来才听说的。
comprehend : 侧重熟悉了解的过程。
- I fail to comprehend their attitude.
我无法理解他们的态度。 - He doesn't seem to comprehend the scale of the problem
他似乎没意识到问题的严重性。 - I'll never comprehend why she did what she did.
我永远也不会明白她为什么那么做。 - I don't think he fully comprehends that she won't be here to help him.
我看他还没有充分意识到她是不会来这里帮他的。
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。
- She explained the whole idea again, but I still didn't understand.
她把整个想法又解释了一遍，但我还是不明白。 - Is there anyone here who understands Arabic?
这儿有人懂阿拉伯语吗？ - We still don't fully understand how the brain works.
我们还未完全弄懂大脑是如何工作的。
