一事不知 Not knowing one thing
Explanation
比喻知识尚有欠缺。
It means that one's knowledge is still lacking.
Origin Story
古时候，有一位读书人，他读了很多书，但是却很自负，认为自己什么都知道。有一天，他遇到一位老先生，老先生问他：“你知道什么是‘一事不知’吗？”读书人傲慢地说：“我读了那么多的书，怎么会一事不知呢？”老先生笑着说：“那你知道什么叫‘一事不知’吗？”读书人哑口无言，这才明白自己虽然读了很多书，但对很多事情却一无所知。
In ancient times, there was a scholar who had read many books, but he was very conceited and thought he knew everything. One day, he met an old gentleman. The old gentleman asked him, “Do you know what it means to ‘not know one thing’?”. The scholar arrogantly said, “I have read so many books, how could I not know one thing?”. The old gentleman smiled and said, “Then do you know what it means to ‘not know one thing’?”. The scholar was speechless and realized that despite all his reading, he did not know many things.
Usage
该成语一般用于形容一个人知识不够全面，或者不懂某件事。
This idiom is usually used to describe someone who does not have comprehensive knowledge or who does not understand something.
Examples
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他虽然学识渊博，但对许多事情一事不知。
tā suīrán xuéshí yuānbó, dàn duì xǔduō shìqing yī shì bù zhī.
He is very knowledgeable, but he doesn't know anything about many things.
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我对于历史一事不知，所以经常向老师请教。
wǒ duìyú lìshǐ yī shì bù zhī, suǒyǐ jīngcháng xiàng lǎoshī qǐngjiào.
I don't know anything about history, so I often ask my teacher.
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这个孩子虽然才5岁，但是对一些事情一事不知。
zhège háizi suīrán cái 5 suì, dànshì duì yīxiē shìqing yī shì bù zhī.
Although this child is only 5 years old, he doesn't know anything about some things.