就是...
Reach for this when you want to say 'it is precisely/exactly that...' — flagging something as the definitive answer, point, or definition. '我喜欢的就是这个.' (THIS is exactly what I like.) Different from the bigger X 就是 Y defining pattern: standalone 就是 at the head of a phrase pins down 'this and only this is the thing.' It carries weight; speakers use it to land an answer firmly.
Structure
就是 [THE THING IN QUESTION]
jiùshì...
How to Think About It
就是 narrows the spotlight to a single answer. 是 alone says 'is'; 就是 says 'is, precisely, no other possibility.' It often answers an unspoken or just-asked question — 'who, which, what?' — and slams the door on alternatives. In casual speech you can use it as a one-word affirmation ('就是!') meaning 'exactly, totally agree.'
Examples
我想要的就是这本书。
Wǒ xiǎng yào de jiùshì zhè běn shū.
This is exactly the book I want.
问题就是钱不够。
Wèntí jiùshì qián bú gòu.
The problem is simply that there isn't enough money.
他就是我说的那个人。
Tā jiùshì wǒ shuō de nàge rén.
He's exactly the person I was talking about.
Common Mistake
Learners scatter 就是 anywhere they want emphasis, but it specifically marks PRECISION/EXCLUSIVITY ('exactly this, nothing else'). Using it just to mean 'also' or 'and' makes the sentence read awkwardly.
我喜欢苹果, 就是香蕉。
我喜欢苹果, 也喜欢香蕉。
Don't Confuse With
X 就是 Y (defining)
When 就是 sits BETWEEN two phrases ('term 就是 explanation'), it's the inline-definition pattern. When it sits at the START of a phrase ('就是这个'), it emphasizes that this is the precise/only answer. Same word, two flavors.
正是 / 恰恰是
正是/恰恰是 carry the same 'exactly this' meaning but in a formal/written register. '这正是问题所在' (This is exactly the problem) is essay-style; '就是这个问题' is conversational.
只是
只是 means 'merely / only' — it diminishes ('it's just a small problem'). 就是 emphasizes ('it's precisely this problem'). Opposite vibes — don't swap them.
Practice
我喜欢的 ___ 这种音乐。
Show answer
就是
问题 ___ 时间太少。
Show answer
就是
Put in order: [就是 / 朋友 / 他 / 最好的 / 我的]
Show answer
他就是我最好的朋友。
Translate to Chinese: 'This is exactly what I wanted.'
Show answer
这就是我想要的。
Identify your favorite thing using 就是.
Show answer
Example answer: 我最喜欢的城市就是上海。 (My favorite city is Shanghai.)