一 (yī)
Normally everybody knows that 一 (yī) means the number one.
For foreign students, they will get shocked by the other uses of 一 (yī).
1, (adj.) same
我们是一个班的。(we are from the same class.)
2, (adj.) whole ; all ; throughout
一路上都是雪。(The whole road was full of snow.)
3, a little
笑一笑,十年少。(A smile prolongs life.)
4,(conjunction) used before a verb or a verbal measure to indicate an action to be followed by a result
她一看到妈妈就哭了。(Once he saw his mom, he cried.)
5, (conjunction) if
一不小心，就回出错。(if you do not pay attention to it, you will get wrong)
一 also has multiple pronunciations.
when you use that alone, or it was used in the end of the word or the sentence, the pronunciation is yī.
十一(shíyī) 五一(wǔyī) 六一(liùyī)
when it comes to the front of other words that has the fourth pronunciation, it is yí.
一半(yíbàn) 一共(yígòng) 一世(yíshì)
when it comes to the front of other words that has the first, second and third pronunciations, it is yì.
一点(yìdiǎn) 一天(yìtiān) 一年(yìnián)
It seems that the character 一 reflects the abundance of Chinese in phonology, grammar and semantics.
Learning a new language is a long trip. we have to practise little by little and day by day.