Usages of yídìng
虽然 他 很 忙， 但是 他 一定 会 来。suīrán tā hěn máng, dànshì tā yídìng huì lái.
Although he is very busy, he will definitely come.
谢谢 你， 我 一定 请 你 吃 晚饭。xièxie nǐ, wǒ yídìng qǐng nǐ chī wǎnfàn.
Thank you; I will definitely treat you to dinner.
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