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肯定 vs 确定 vs 一定 (sure / certain)
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How sure are you?
- Your friend asks if the train leaves at eight. You checked the ticket twice.
- I / me我sure确定to be / is是八点，you你necessarily一定want / will / need要早点儿to / arrive到。 — "I'm sure it's eight; you really must get there early."
necessarily一定 = certainly, must
- necessarily一定 + verb = certainly will / must: he他necessarily一定can / will会to come来, you你necessarily一定want / will / need要to go去.
- not不necessarily一定 = not necessarily: expensive贵(ones)的not不necessarily一定good好.
expensive贵(ones)的not不necessarily一定good好。
“Expensive things aren't necessarily good.” Which fits? 贵的____好。
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不一定 means “not necessarily”: 贵的不一定好. 一定不 means “definitely not”, which is a different claim, and 不确定 / 不肯定 mean “unsure”.
definitely肯定 = definitely (confident judgement)
- definitely肯定 = definitely, surely: he他definitely肯定forgot忘(completed / change)了 — "He's definitely forgotten."
- It can also be an adjective / verb of affirming: teacher老师definitely肯定(completed / change)了I / me我(ones)的way of thinking想法 — "The teacher approved my idea."
he他definitely肯定forgot忘了。
老师肯定了我的想法 means the teacher approved my idea.
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肯定 can be a verb meaning “affirm”.
sure确定 = be sure, confirm (a verb)
- sure确定 is a verb: be sure of, confirm, fix: you你sure确定(yes/no ?)吗？ — "Are you sure?" (concept of) time时间still / also还not / haven't没sure确定 — "The time hasn't been fixed."
- sure确定 does not go before another verb as "certainly": he他necessarily一定can / will会to come来, not he他sure确定can / will会to come来 in that sense.
Ask: “Are you sure?” 你____吗？
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确定 is the verb “be sure”.
Which word when?
- Predicting or requiring: necessarily一定 (necessarily一定want / will / need要, necessarily一定can / will会). Guessing confidently: definitely肯定.
- Checking or deciding: sure确定 (sure确定(concept of) time时间, I / me我not不sure确定).
you你sure确定吗？
Match each sentence to its meaning.
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一定 = must, 肯定 = definitely, 确定 = fix / be sure.
Recap
- necessarily一定 = must / certainly (not不necessarily一定 = not necessarily). definitely肯定 = definitely (confident guess; also "affirm").
- sure确定 = be sure / confirm / fix (a verb).
Read the full reference: HSK 4 grammar — Comparing similar functions.
Your friend asks if the train leaves at eight. You checked the ticket twice. Close the examples. Say a Mandarin response, then write it in Chinese. Explain briefly in English what the lesson’s pattern adds. Compare with the model, then change one detail and try again.
This is supported productive practice. Compare meaning and structure; your answer need not copy the model. A partner or teacher must hear the spoken response to comment on pronunciation.