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fùcí: yídìng
Adverb 一定 (副词：一定)
一定 means 'definitely' or 'must.' Put it before a verb or modal verb to show strong certainty, a firm promise, or a confident guess.
Anchor example
明天的考试很重要，我一定去。
Míngtiān de kǎoshì hěn zhòngyào, wǒ yídìng qù.
Tomorrow's exam is important. I will definitely go.
HSK 2
HSK 2
1
1 structures
10
10 exercises
Lesson summary
一定 means 'definitely' or 'must.' Put it before a verb or modal verb to show strong certainty, a firm promise, or a confident guess.
一定 is used when the speaker is very sure. It can be a promise: 我一定来, a requirement: 你一定要休息, or a confident guess: 他一定在家. It is stronger than 应该 and 可能. In negative sentences, 一定不 means 'definitely not,' while 不一定 means 'not necessarily'; these two are very different.
Grammar pattern
Subject + 一定 + Verb / 一定要 + Verb
Expresses certainty, a firm promise, or strong advice/requirement.
明天的考试很重要，我一定去。
Míngtiān de kǎoshì hěn zhòngyào, wǒ yídìng qù.
Tomorrow's exam is important. I will definitely go.
你生病了，一定要多喝水。
Nǐ shēngbìng le, yídìng yào duō hē shuǐ.
You are sick. You must drink more water.
这么晚了，他一定在家。
Zhème wǎn le, tā yídìng zài jiā.
It is so late. He must be at home.
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