Both words kinda mean “must, necessarily, certainly”. Can someone explain the differences between the two?

  • Are you asking what is the difference between '必定' and '一定' or the difference between '必' and '定'? – Tang Ho Nov 28 '18 at 8:24
  • They are the same meaning. But I said "一定" more than "必" , "必然", "必定" in general. – AechoLiu Dec 19 '18 at 8:34

Since you are not asking what is the difference between '必定' and '一定' or the difference between '必' and '定', I would just go ahead and state the difference between '必' and '一定'

From my answer to this question:

Meaning of 的 and 之 when both are used in the same sentence

之 is the classical Chinese counterpart of 的 in modern Chinese

必 is the classical Chinese counterpart of 一定/必定 in modern Chinese


Classical Chinese style: "兵家()爭之地"

Modern Chinese: "軍事決策者(一定/ 必定)會去爭奪的地點"


Classical Chinese style: "中此毒者()死"

Modern Chinese: "中了這個毒的人(一定/必定)會死亡"


Classical Chinese style: "日軍稱三月內()亡中國"

Modern Chinese: "日本軍方宣稱三個月內(一定/必定)能覆亡中國"

'必' on its own has other meaning and usage, but the question only asked for the comparison between '必' and '一定'. The most obvious difference between the two is as this answer stated.

Notice: Actually, I should say '必' is more literary and '一定' is more colloquial because classical style wording appear mostly in writing

  • Are they classical Chinese? Not just formal form? – 炸鱼薯条德里克 Nov 28 '18 at 13:11
  • @神秘德里克 Classical Chinese style is embedded in modern Chinese. We don't often hear pure classical speech, but classical style phrases appear in writing a lot. Day to day conversation is made up of 'colloquial, literary, classical phrases and slang' – Tang Ho Nov 28 '18 at 13:17
  • @神秘德里克 1."請老師(垂鑒)" 2. "請老師(過目)" 3.請老師(看看). -- 垂鑒 is a formal term (to show respect), 過目 is a literary term (base on classical style) , 看看 is a colloquial term. The sentence: "天津是兵家必爭之地" is a mix of classical and standard Chinese, and it is totally normal in modern Chinese writing and speech. But it is not considered 'formal form' – Tang Ho Nov 28 '18 at 13:46

It is the same, you can interchange the two.

  • 1
    Yes, they mean the same, but they are for different styles (literary and colloquial), you cannot freely interchange them. When you replace '必' with '一定' , you have to change the rest of the sentence sometimes. For example: "(必)無好果" = "(一定)沒有好結果" ; you cannot just replace '必' with '一定' and write " 一定無好果" – Tang Ho Nov 28 '18 at 17:07
  • 我必须去 I must go there (because of some reasons).
  • 我一定去 I must go there (really want to, no matter what) .

They all mean you must go there sometime in the future.

However, 一定 is subjectively, 必 is objectively.

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