一口咬定 insist
Explanation
这个成语形容一个人固执己见，坚持自己的说法，即使面对事实证据也不肯承认错误。
This idiom describes a person who is stubborn and sticks to their own statement, refusing to admit mistakes even in the face of factual evidence.
Origin Story
传说，古代有一个贪婪的富商，他为了积累更多的财富，想方设法克扣员工的工资。一天，他的一个伙计发现账目上有问题，便质问富商。富商面对伙计的质问，狡辩道：“你少胡说，这些账目都是我亲自核对的，绝对不会错！”伙计将账目仔细地分析了一遍，发现富商的确动了手脚。他再次质问富商，富商还是一口咬定，说：“我根本没有动过账目，是你自己看错了！”伙计气愤地指着账目说：“这明明就是你动了手脚，怎么还敢狡辩？”富商仍然不承认，一口咬定说：“是我看错了，是我看错了！” 伙计无奈，最终只能认栽。
Legend has it that in ancient times, there was a greedy merchant who, in order to accumulate more wealth, found ways to deduct the wages of his employees. One day, one of his employees noticed a problem with the accounts and questioned the merchant. The merchant, faced with his employee’s questioning, argued: “You’re talking nonsense. I personally checked these accounts, there’s absolutely no mistake!” The employee carefully analyzed the accounts and found that the merchant had indeed manipulated them. He questioned the merchant again, but the merchant still insisted that he was innocent. He said: “I didn’t touch the accounts at all, you’re the one who’s wrong!” The employee angrily pointed at the accounts and said: “It’s clear that you manipulated these accounts, how dare you deny it?” The merchant still refused to admit it, insisting: “I was wrong, I was wrong!” The employee was helpless and could only accept it in the end.
Usage
当一个人坚持自己的说法，不承认错误的时候，可以用“一口咬定”来形容。
When someone insists on their own statement and refuses to admit mistakes, you can use “一口咬定” to describe this.
Examples
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面对质问，他一口咬定自己没有偷东西。
miàn duì zhì wèn, tā yī kǒu yǎo dìng zì jǐ méi yǒu tōu dōng xī.
Faced with questioning, he insisted that he did not steal anything.
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他一口咬定是朋友借的，坚决否认自己偷了钱。
tā yī kǒu yǎo dìng shì péng yǒu jiè de, jiān jué fǒu rèn zì jǐ tōu le qián.
He insisted that his friend borrowed it and vehemently denied stealing the money.
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不管怎么解释，他都一口咬定这是他的功劳。
bù guǎn zěn me jiě shì, tā dōu yī kǒu yǎo dìng zhè shì tā de gōng láo.
No matter how he explained it, he insisted that it was his merit.
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尽管证据确凿，他还是一口咬定自己无辜。
jǐn guǎn zhèng jù què záo, tā hái shì yī kǒu yǎo dìng zì jǐ wú gū.
Despite the irrefutable evidence, he still insisted on his innocence.
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她一口咬定是自己做的决定，不听任何人的意见。
tā yī kǒu yǎo dìng shì zì jǐ zuò de jué dìng, bù tīng rèn hé rén de yì jiàn.
She insisted that it was her own decision and would not listen to anyone else.