I always knew, from my studies of Japanese, that the number two is 二 (èr). I am not sure about the actual etymology, but looking at the character, it's understandable why it represents the number "2".

Recently, I discovered that there is another character that represents the same number. That character is 两 (liăng).

According to my textbook:

  1. 二 is used when telling or writing a "meaningless" number, such as a telephone number, a zip code, etc;
  2. 两 is used together with nouns, such as in "two students" = 两个学生.

Is this correct in current Mandarin? If so, does this mean that 二个学生 is just plain wrong or that Chinese people would give me a weird look if I said it?

Are there other situations in which the use differs or is it interchangeable? I found a site, nciku.com, where there are notes about it, but it says what I already know more or less, so I am asking if there is something else.

Lastly, what's the etymology, if available, for 两?

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    Not related to your questions: Do you know that 1 can sometimes be read as "幺(yāo)"? Like 110 -- 幺幺零. (Or maybe I should put this in chat) – fefe Jan 9 '12 at 10:30
  • Ah, I didn't know about that! Actually, you should leave it here, it's more than related. Are there other cases? If you want we can include it in this question, if this is the only other case... Adding too much cases would change the question... :D – Alenanno Jan 9 '12 at 10:32
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    In Mainland China, when reading out numbers, 幺(yāo) is almost always used. I think this may have a military origin. Taiwanese people apparently find it quite strange. – Bathrobe Jan 9 '12 at 13:40
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    To add further to the above; 幺(yāo) is commonly heard when people read out their phone numbers. – going Jan 9 '12 at 22:21
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    I believe 幺 is used as 一 sounds like 七 and is easily confused. It may be similar to the use of "zwo" in German or "niner" in military radio comms. – March Ho Jun 7 '15 at 19:56

Rather than saying that 两 is used with nouns, I would say that 两 is used with measure words. If you use any type of measure word with the number 2, use 两. For convenience, I've identified 3 types of measure words:

  1. Standard measure words, e.g. 两个人、两本书、两棵树.

  2. Numbers that are larger than 100, e.g. 两百, 两千三百六十二. 百, 千, and 万 can be seen as a sort of measure word.

  3. Time, e.g. 下午两点. Again, 点 functions as a type of measure word here.

二 is used when counting without measure words, such as in telephone numbers, metro lines (二线), addresses, etc.

  1. ordinal, e.g. 第二个, 二哥. when you want to say the second, you can only use 二, it is wrong to say that 第两个.
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    下午两点 = It's 2 PM? By the way, I removed all of that bold. Too much MarkUp isn't nice to be seen... :D – Alenanno Jan 9 '12 at 19:18
  • Yes, it means 14:00. I've edited a bit more to make the numbering internally consistent with the content. – Bjorn Jan 9 '12 at 20:40
  • This contradicts Mark's answer which I believe to be correct. 第二 clearly contains a measure word. The difference is in the cardinal or ordinal nature, and not the presence or absence of a measure word. – March Ho Jun 7 '15 at 20:00
  • 二百 is also correct though. – Jacob de Neur Nov 19 '18 at 11:04

二 (èr) is used (with nouns), if you are talking about their order, but if you are counting how many, 两 (liăng) is used (also with nouns). Stated concisely:

  • 两 (liăng) is a cardinal number, as in, 两个 (liăng-ge) 'two of something.'
  • 二 (èr) is an ordinal number, as in, 第二个 (dì èr-ge) 'the second thing.'

Perhaps more common in speech are the cardinal numbers, as in, 'I'll have two bowls of rice.' Both cardinal and ordinal numbers use measure words.

Chinese is immensely weak on grammatical inflection, so two/second, an extremely important number (perhaps the most important number? thinking about odd or even) is the only number that it inflects in this way. English inflects all numbers.

If you think, 'second' (二) or 'two' (两) you'll be all right.

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For ordinal numbers use 二 as in 第二个小孩 or 第二天

If you are counting out loud it is perfectly fine to count 一， 二， 三， 四，五 etc.

However, if you include a MW it should be 一个， 两个， 三个 etc.

There are also some other special 2 words in Chinese:

一对 yí duì - A pair


一双 yì shuāng- A pair


also pronounced èr is used to represent the number 2 on items to prevent forgery such as on cheques.

There is also pronounced yǐ which is the 2nd Heavenly Stem and is used to represent 2 or 2nd in some rare cases. See the linked article for some modern uses.

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Good question and a little complex to answer. Previous answers seem good, and I want to make a conclusion based on them. Basically, 两 and 二 mean two, but either of them are used in some other cases, where they are not interchangeable.

  1. When counting (with single character), only 二 is used. You would hear "一二三四，二二三四..." as a melody when some is doing exercise.

  2. I agree with the viewpoint from MarkDBlackwell's answer and the measure word is a very rough standard to distinguish 二 and 两. Examples:

    两天 (two days), 两夜 (two nights), 两次 (twice,two times), 两广 (short for 广东 and 广西 provinces. Note that there is no measure words in these cases), 第二天 (the second day), 二号(the second day, as in 三月二号 — march 2nd), 两个苹果（two apples), 第二个苹果 (the second apple), 二等 (the second class), 二婚 (the second marriage), 两度 (two times), 二度 (the second time).

  3. 二 could mean "one another,different". Examples:

    二心 (literal meaning: one another heart, different heart". Meaning "disloyalty"), 二话 (literal meaning: one another words, different words. Meaning "disagreement, objection").

  4. 两 could mean "both, either". Examples:

    两侧 (both sides), 势不两立 (to be irreconcilable with), 两边 (both sides), 两端 (both ends), 两极 (both poles).

  5. In a serial number (phone number) or code (barcode, etc.), only 二 is used.

  6. In science, 二 is often used. Examples:

    二项式 (binomial), 二氧化碳 (CO2)，三氧化二铝 (Al2O3), 二次曲线(curve of the second degree), 二元方程 (two element equation), 二阶微分方程 (two order differential equation).

  7. In numbers, when two is used at the digit fewer than hundred, only 二 is used. In other cases, 两 could also be used (they are interchangeable). Examples:

    25 二十五, 12 十二, 22 二十二, 2.22 二点二二. 222.22 两百二十二点二二 or 二百二十二点二二.

But there are some other cases, that don't follow the rules above. You may need to memorize them.


Idioms: 说一不二, 三心二意, 三言两语, 三三两两, 二人世界(the world only contains you and your love)

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Besides meaning "two" and "second", "二" has another meaning in spoken Chinese, that is "stupid". For example: "他很二" means "he is stupid".

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    二 is stupid in a careless way, i.e., foolhardy or rash. – Wang Dingwei Dec 3 '14 at 8:50

The difference between the two words lies in the following set of magical rules:

1. Use 二 (èr) when reading numbers and numbers in sequence, but 两 (liǎng) in front of 千 (qiān, thousand), 万 (wàn, ten thousand) and 亿 (yì, a hundred million).


(1) Wǒ yǒu èrshí gè píngguǒ.

我   有   二十 个    苹果。
I have twenty apples.

(2) Wǒ de chēpái hàomǎ shì líng èr wǔ qī.

我   的   车牌    号码    是   零  二 五 七。

My license plate number is 0257.

(3) Wǒ yǒu liǎngqiān kuài qián.

我   有     两千      块    钱。

I have two thousand Yuan.

2. Use 两 (liǎng) before classifiers such as 两年 (liǎngnián, two years), 两岁 (liǎngsuì, two years old), and 两本 (liǎng běn).


Wǒ yǒu liǎng běn shū.

我 有 两 本 书。

I have two books.

3. Put 二 (èr) directly before nouns to express “second.” For example, 二楼 (èr lóu) means the second floor.


Wǒ zhù zài èrlóu.

我 住 在 二楼。

I live on the second floor.

4. Use 二 (èr) to refer to something second-hand or not brand new such as 二手房 (èrshǒu fáng, second-hand house), 二手车 (èrshǒu chē, second-hand car).


Wǒ mǎi le yíliàng èrshǒu chē.

我 买 了 一辆 二手 车。

I bought a second-hand car.

Hope it can help you.

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Your textbook is correct. Chinese people will never say or write 二个学生. 两个学生 is the correct way.

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The answer of user3408789 seems to be incorrect, or at least, not complete.

I live in Shanghai and here, in most cases, 10两=1斤=500g

When measuring medicine (中药), 16两=1斤 and I am not sure if 1斤 is 500g in this circumstance.

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Another case: 二两肉. It means 100g of meat here, but not twenty-two (g) meat!

In such cases, 两 is used as measurement unit - 50 grams.

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    I'd buy any meat from you because in my place 一两 is only 50 grams. – Wang Dingwei Dec 3 '14 at 8:43
  • Oh, what a stupid mistake – when.soul Dec 5 '14 at 1:20
