In Chinese, there are two words for “two”: 二（èr) and 两(liǎng), and Chinese learners are often confused by which one they should use. Today, we will illustrate the correct ways to use each of them.
The biggest different between them is that “二” (èr) is used generally when counting in numbers (one, two, three,…), or performing mathematical functions.
However, when you want to say “two of” something, 两(liǎng) is used in front of measure words to express a quantity. This is similar in English to saying “a pair” of something, but it is used in Chinese to express having “two of” almost anything, for example:
两个小时(liǎng gè xiǎo shí) two hours;
两天(liǎng tiān) two days;
两个星期(liǎng gè xīng qī) two weeks;
两个月(liǎng gè yuè) two months.
There is one potentially confusing example. Instead of saying 二点(èr diǎn) to express 2 o`clock, the correct way to express this is actually 两点(liǎng diǎn) 2 o’clock – you can think of it literally as a quantity of “two points on the clock.”
Let’s see other differences between them in use.
1) 二 （èr) is used as an ordinal number, such as 第二(dì èr) the second， 二楼(èr lóu) the second floor，etc.
2)When used in math to indicate a numeral, a fraction, or a decimal，“二 ”is used instead of “两”.
1/2(èr fēn zhī yī) 二分之一; 1/3(sān fēn zhī èr) 三分之二
0.2(líng diǎn èr) 零点二； 2.4(èr diǎn sì) 二点四
3) In the multi-digit numbers, use 二，not 两for tens place and ones place, as 22(二十二). Before the百(hundred)’s place, either 两 or 二 can be used, as in 200(二百/两百). When used before the “千”(qiān ,thousand)、“万”(wàn, ten thousand) or “亿”(yì, hundred million) places, “两” is much more frequently used.
E.g. 2000(两千); 22222(两万两千二百二十二); 200000000(两亿)
4) Before “traditional” units for capacity or weight (尺(chǐ)/亩(mǔ)/升(shēng)…), both 两 and 二 can usually be used. For example: 二尺/两尺(èr chǐ /liǎng chǐ)； 二亩/两亩(èr mǔ /liǎng mǔ)； 二升/两升(èr shēng /liǎng shēng).
However, before the “new” units for capacity and weight, typically 两，is used. For instance: 两吨 and 两公里.
Note that两 also means 1/20 of a kilogram, so to make this distinction clear, two “1/20 kilo” is represented as 二两 (èr liǎng )， not 两两 (liǎng liǎng).
5) When you want to approximate a number, you can use “两”and either “一”/“三” together in succession. For examples
一两天(yī liǎng tiān) One or two days.
这个词我们学了两三次了. (Zhè ge cí wǒ men xué le liǎng sān cì le.)
We’ve studied this word two or three times.
每个人要花两三百块钱。 (Měi gè rén yào huā liǎng sān bǎi kuài qián.) Every one needs to spend two to three hundred RMB.
6) “两”is also often employed on its own to indicate a generally small number of quantity, whereas “二” can not be used in this way. For example:
怎么就来了这么两个人?( zěn me jiù lái le zhè me liǎng gè rén ?)
How have so few people come?
“俩(liǎ)” means “两个”, and is more commonly used as a colloquial term in northern China. Some examples: 我们俩(我们两个, the two of us), 俩苹果(两个苹果, two apples).
Note that贰 (also pronounced èr) is used to represent the number 2 on items like cheques to prevent forgery.
Now, hopefully it is a little more clear when to use 两 and 二!