半 vs 一半 (bàn vs yíbàn): half as a prefix vs half as a noun
半 and 一半 both express the concept of 'half', but they are used differently. 半 is a prefix that attaches directly to measure words (e.g., 半个 'half a unit'), while 一半 is a standalone noun meaning 'one half' and can be followed by 的 to modify nouns (e.g., 一半的人 'half of the people'). Choosing the wrong form can produce ungrammatical phrases like *一半个 or *半人.
半 (bàn) functions as a prefix that attaches directly to measure words or time units to mean 'half a [unit]', e.g., 半个 'half a unit' (of a countable noun) or 半天 'half a day'. It cannot stand alone as a noun. 一半 (yíbàn) is a noun meaning 'one half', used to refer to a half of a whole. It can be followed by 的 to modify a noun (e.g., 一半的水 'half of the water') or used as an object (e.g., 吃了一半 'ate half'). 一半 never directly precedes a measure word; the correct expression for 'half a [unit]' is 半 + measure word.
When to use each
Use 半 directly before a measure word to indicate 'half of a unit'. For example, 半个苹果 means 'half an apple'. 半 can also attach to time words (e.g., 半年 'half a year') and other standard units (e.g., 半斤 'half a catty'). It is never used as a standalone noun; it must always precede a measure word or noun in fixed patterns.
半 can also appear in expressions like 半……半…… (e.g., 半信半疑 'half-believing, half-doubting'), but those are idiomatic. In the fraction sense, it is always attached to a measure word.
Use 一半 as a noun to refer to 'half of something'. It can stand alone as the subject or object of a sentence. When modifying a noun, add 的 after it (e.g., 一半的人 'half of the people', 一半的时间 'half of the time'). 一半 can also follow 的 to indicate 'half of that' (e.g., 其中的一半 'half of it').
一半 already contains the number 一, so it is never preceded by another 一. For example, *一一半 is incorrect. When you mean 'half a [measure word]', do not use 一半; use 半 + measure word instead.
At a glance
| 半 | 一半 | |
|---|---|---|
| Part of speech | Prefix (attaches to measure words) | Noun |
| Usage before measure words | Directly, e.g., 半个 (bàn ge), 半年 (bàn nián) | Cannot directly precede measure words; use 半 + measure word instead |
| Usage before nouns | Only when attached to a measure word that then modifies a noun, e.g., 半个苹果 (bàn ge píngguǒ) | Must be followed by 的 before the noun, e.g., 一半的苹果 (yíbàn de píngguǒ) |
| Standalone as noun | No (cannot be subject/object by itself) | Yes (e.g., 一半就够了 'Half is enough') |
| Example: half of the water | 半杯水 (bàn bēi shuǐ) 'half a glass of water' | 一半的水 (yíbàn de shuǐ) 'half of the water' |
Examples
- 半我吃了半个苹果。Wǒ chī le bàn ge píngguǒ.I ate half an apple.半 + measure word (个) = half a unit.
- 一半一半的苹果是坏的。Yíbàn de píngguǒ shì huài de.Half of the apples are bad.一半 + 的 modifies the noun 苹果.
- 半他等了我半天。Tā děng le wǒ bàntiān.He waited for me half a day.半 attaches to time word 天.
- 一半他分给我一半。Tā fēn gěi wǒ yíbàn.He gave me half.一半 as object, standalone.
- 一半✗一半个苹果不好吃。✗ Yíbàn ge píngguǒ bù hǎochī.✗ Half an apple is not tasty.Incorrect: 一半 cannot directly precede a measure word. Correct: 半个苹果.
Common mistakes
- Using 一半 directly before a measure word (e.g., *一半个 → should be 半个).
- Using 半 as a standalone noun (e.g., *半的人 → should be 一半的人).
- Adding an extra 一 before 一半 (e.g., *一一半 → redundant, 一半 already means 'one half').
- Omitting 的 when 一半 modifies a noun (e.g., *一半水 → should be 一半的水).
FAQ
- When do I use 半 vs 一半?
- Use 半 when you want to say 'half a [unit]' – it attaches directly to a measure word (e.g., 半个, 半年). Use 一半 as a noun to refer to 'half of something' – it can stand alone or be followed by 的 to modify a noun (e.g., 一半的时间 'half of the time').
- Can I say 一半个 to mean 'half a'?
- No. 一半 cannot directly precede a measure word. The correct expression is 半 + measure word: 半个 'half a unit', 半年 'half a year'. If you need to use 一半, you must add 的: 一半的 [noun] (e.g., 一半的苹果 'half of the apples').
- How do I say 'half of the people'?
- Say 一半的人 (yíbàn de rén). 半 alone cannot be used this way; *半的人 is wrong. For 'half a person', say 半个人 (bàn ge rén), which means 'half a person' (e.g., figuratively).
- Can 半 be used without a measure word?
- In standard Mandarin, 半 must be followed by a measure word or a time unit (e.g., 半杯, 半天). It cannot stand alone. In some fixed expressions like 半路 (bàn lù 'halfway'), 半 is part of a compound word, but those are not uses of 半 as a fraction prefix.