半 (Half) | Chinese (Mandarin) Grammar

半 (bàn) is the Chinese word for "half," but it splits into two grammatical lives that English blurs into one. As a quantity, 半 behaves like a number — "half a(n) _" — and, like any number, it needs a measure word: 半个 (bàn ge), 半年 (bàn nián). As a noun, the compound 一半 (yíbàn) means "one half, 50%, half of it" and stands on its own with nothing after it. English uses the single word "half" for both jobs — half an apple and I ate half — so the number-one skill on this page is telling 半 (half a unit) from 一半 (half of the whole). The mechanical detail of where the measure word sits lives on the companion page, 半 with a measure word; here we focus on the quantity itself and on 半 vs 一半.

半 = "half a unit": it counts, so it needs a measure word

Treat 半 exactly like the number 一. Just as you'd never say 一苹果 without a classifier, you don't say 半苹果 either — it's 半个苹果 (bàn ge píngguǒ), "half an apple." The reason is the same reason measure words are obligatory after any number: 半 occupies the number slot, and that slot pulls a classifier behind it.

给我半杯就行，我不太渴。

gěi wǒ bàn bēi jiù xíng, wǒ bú tài kě

Just half a cup for me — I'm not that thirsty. (informal) — 半杯, half a cup, with the classifier 杯.

他半个字都没说就走了。

tā bàn ge zì dōu méi shuō jiù zǒu le

He walked off without saying a single word. (informal) — 半个字, literally 'half a word', an idiom for 'not one word'.

A few time nouns — 年 (year), 天 (day), 分钟 (minute) — are their own measure words, so 半 attaches with nothing in between: 半年, 半天, 半分钟. Others, like 小时 (hour), need 个: 半个小时.

我学中文快半年了，还是听不太懂。

wǒ xué Zhōngwén kuài bàn nián le, háishì tīng bú tài dǒng

I've been learning Chinese for almost half a year and still can't follow much. (informal) — 半年 attaches directly; 年 is its own measure word.

For the "one and a half" pattern (一个半, 两个半 — where 半 jumps to after the measure word), and for the full placement rules, see 半 with a measure word. One preview so it isn't a surprise:

这部电影差不多演了一个半小时。

zhè bù diànyǐng chàbuduō yǎn le yí ge bàn xiǎoshí

The movie ran for about an hour and a half. (informal) — 一个半, whole unit first, then 半.

一半 = "half of it": the standalone noun

一半 (yíbàn) is a noun meaning "one half" — half of some whole you already have in mind. Unlike 半, it takes no measure word and no noun immediately after it in the object slot; it points back at a known thing. You eat half an apple (半个苹果), but you eat half of this apple (这个苹果吃了一半).

作业我只写了一半，剩下的明天再说。

zuòyè wǒ zhǐ xiě le yíbàn, shèngxià de míngtiān zài shuō

I've only done half my homework; the rest can wait till tomorrow. (informal) — 一半, half of the (known) homework.

这笔钱一半是我的，一半是他的。

zhè bǐ qián yíbàn shì wǒ de, yíbàn shì tā de

Half this money is mine, half is his. (neutral) — the 一半…一半… frame splits a whole in two.

When you do want a noun after it — "half of the students," "half the seats" — 一半 links to the noun with 的: 一半的学生, 一半的座位. The 的 is what marks it as "half of [that noun]."

今天班里一半的同学都请假了。

jīntiān bān li yíbàn de tóngxué dōu qǐngjià le

Half the class is out sick today. (neutral) — 一半的 + noun for 'half of the ___'.

💡

Quick decision: if the next word is a unit you're measuring out (个, 杯, 瓶, 年…), use bare 半 — 半个, 半年. If you mean half of a whole already on the table and nothing (or 的 + noun) follows, use 一半. "Half an apple" = 半个苹果; "half of the apple" = 苹果的一半 / 吃了一半.

The idiomatic 半: "a long while," "most of it"

Because 半 sits at the exact midpoint, it has bred a cluster of idioms where it no longer means a clean 50%. The most common is 半天 (bàntiān) — literally "half a day," but in speech it means "a long while, ages":

这个问题我想了半天，也没想出答案。

zhège wèntí wǒ xiǎng le bàntiān, yě méi xiǎng chū dá'àn

I puzzled over this for ages and still couldn't come up with an answer. (informal) — 半天 = 'a good while', not literally 12 hours.

Two more high-frequency ones: 一大半 (yí dà bàn), "the bigger half / most of it," and 多半 (duōbàn), "for the most part / probably."

蛋糕被孩子们吃了一大半。

dàngāo bèi háizimen chī le yí dà bàn

The kids ate most of the cake. (informal) — 一大半, the greater portion.

他还没回消息，多半是睡着了。

tā hái méi huí xiāoxi, duōbàn shì shuìzháo le

He hasn't texted back — he's probably fallen asleep. (informal, colloquial) — 多半 = 'most likely'.

一半 vs the formal fraction 二分之一

In everyday speech "one half" is 一半. In math, science, or careful written registers, the same value is the true fraction 二分之一 (èr fēn zhī yī) — built on the denominator-first pattern covered on the fractions page. Note it uses 二 (the math digit), never 两.

实验成功的概率大约是二分之一。

shíyàn chénggōng de gàilǜ dàyuē shì èr fēn zhī yī

The probability of the experiment succeeding is about one half. (academic) — the formal fraction 二分之一 for 1/2.

For clock time, "half past" also uses 半, placed after 点: 两点半 (half past two) — see the clock time page.

Common Mistakes

1. Using bare 半 to mean "half of it." For "I ate half (of the whole)," you need the noun 一半, not the quantifier 半.

❌ 苹果我吃了半。

Incorrect — for 'I ate half of it' use 一半: 苹果我吃了一半.

✅ 苹果我吃了一半。

píngguǒ wǒ chī le yíbàn

I ate half of the apple.

2. Blending 一半 with a measure word. 一半 is a standalone noun; it can't take 个 the way 半 does.

❌ 我要一半个苹果。

Incorrect — 'half an apple' is 半个苹果; 'half of the apple' is 苹果的一半. Don't mix them into 一半个.

✅ 我要半个苹果。

wǒ yào bàn ge píngguǒ

I'd like half an apple.

3. Using 两 in the formal fraction for one half. The written fraction is 二分之一 — the digit 二, never 两.

❌ 两分之一

Incorrect — the fraction 1/2 is 二分之一; 两 is only for counting things.

✅ 二分之一

èr fēn zhī yī

one half (as a written fraction).

4. Reading 半天 literally. In conversation 半天 usually means "ages," not exactly twelve hours.

❌ 我等了半天。

Don't take it literally — in speech 半天 means 'ages', not 'half a day / twelve hours'. The sentence is fine; the literal reading is the error.

✅ 我等了半天，他才来。

wǒ děng le bàntiān, tā cái lái

I waited ages before he finally showed up. — 半天 = 'a long while'.

Key Takeaways

半 = "half a unit" and behaves like a number, so it takes a measure word: 半个苹果, 半杯, 半年. Placement rules (including 一个半) live on 半 with a measure word.
一半 = "half of it, 50%," a standalone noun — no measure word; add 的 before a noun (一半的学生).
The split mirrors English half an apple (半个苹果) vs. half of the apple (苹果的一半 / 一半) — Chinese forces you to pick.
Idiomatic 半: 半天 = "ages," 一大半 = "most of it," 多半 = "probably."
The everyday "half" is 一半; the formal written fraction is 二分之一 (with 二, not 两).

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