一定 (yīdìng) — certainly / a certain

HSK 3 | adverb / adjective | certainty or a fixed amount

一定 (yīdìng)

Used as an adverb meaning "certainly/definitely," or as an adjective meaning "a certain (amount/degree)."

Meanings

  1. [adverb] Certainly, definitely, surely.
  2. [adjective] A certain, a fixed, a particular (amount or degree).

Example Sentences

你一定要好好学习。 Nǐ yīdìng yào hǎohǎo xuéxí. You must study hard (for certain).

这件事一定很重要。 Zhè jiàn shì yīdìng hěn zhòngyào. This matter is certainly very important.

学好中文需要一定的时间。 Xué hǎo zhōngwén xūyào yīdìng de shíjiān. Learning Chinese well requires a certain amount of time.

他一定已经到家了。 Tā yīdìng yǐjīng dào jiā le. He has certainly already arrived home.

Collocations

Collocation Meaning
一定要 must, have to
一定会 will certainly
一定的 a certain (modifier)
一定程度 a certain degree/extent
不一定 not necessarily

Memory Hook

Think of 一 (one) and 定 (fixed/settled): once it is set to "one," the outcome is fixed — it is certain.