对牛弹琴 playing the lute to a cow
Explanation
这个成语比喻对没有理解能力的人讲道理，如同对着牛弹琴一样，毫无效果。
This idiom means talking to someone who is incapable of understanding is like playing music to a cow, it is ineffective.
Origin Story
古代音乐家公明仪每次弹琴时，他的琴声引来很多鸟儿与蝴蝶。当看到水牛在吃草，就对水牛弹奏几曲，结果水牛无动于衷地走开，公明仪大叹：“对牛弹琴，一窍不通。”后来人们就用“对牛弹琴”来比喻对不懂得的人讲道理，如同对着牛弹琴一样，毫无效果。
The ancient musician Gongmingyi often played music that attracted many birds and butterflies. One day, when he saw a cow grazing, he played a few melodies for it. The cow, however, walked away unmoved. Gongmingyi sighed:
Usage
这个成语比喻对没有理解能力的人讲道理，如同对着牛弹琴一样，毫无效果。
This idiom is used to describe explaining something to someone who is incapable of understanding, which is compared to a pointless attempt to play music to a cow.
Examples
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跟他说道理，真是对牛弹琴，他根本听不进去。
gen ta shuo dao li, zhen shi dui niu tan qin, ta gen ben ting bu jin qu.
It's like talking to a brick wall trying to reason with him.
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不要再跟他解释了，简直是对他牛弹琴，他不会明白的。
bu yao zai gen ta jie shi le, jian zhi shi dui ta niu tan qin, ta bu hui ming bai de
Don't bother explaining it to him anymore. It's like talking to a wall, he won't understand it.