“二” and “两” are literally the same but can’t be always used interchangeably. What is the difference between “二” and “两”?
1. to number: 一，二，三 ~ one, two, three ~
2. decimals and fractions: 六点二 6.2
3. used for an ordinal number: 第二 the second
4. used with measure words: 二英尺 two feet
5. the last item for multi-bit figures: 二百二十二 two hundred and twenty two
1. two: 两万元 two thousand people
2. both (sides); either (side): 两面 both sides
3. a unit of weight：二两茶叶 two liang of tea
4 some; a few: 说两句 say a few words;
“二” and “两”, which one to use？
1. When 二 and 两 are used together to express an approximate number, for basic unit, you can only say 两三~; for tens digit，you can only say 十二三~，二三十~; in other cases, you can use either 二 or 两, e.g. 二三百/两三百~，二三万/两三万~.
2. 二 can be used only before traditional measure words such as 尺, 寸，里，亩，两，斤，etc, but 两 can be used before almost all the measure words. Therefore, you can’t say 二台机器, 二双鞋，二张桌子, etc because 台, 双, 张, etc are not traditional measure words.
3. 二 can be used as ordinal number, e.g. 第二 the second，二楼 the second floor but 两 can not.
4. 二 can be used in fractions and decimals but 两 can not, e.g. 1/4 四分之二，3.2 三点二, etc.