The short form of 'who is' or 'who has'. Both are written the same way, so you have to look at what comes next to know which one it is.

'who is' or或 'who has' The short form of的縮短形式。Both兩種 are written the same way寫起來一模一樣, so所以 you你 have to look at what comes next得看後面接什麼 to know which one it is才知道是哪一個。

'Who's your teacher?' is 'who is'. 'Who's taken my pen?' is 'who has', because 'taken' is a past participle.

'Who's your teacher?'你的老師是誰？ is是 'who is'。'Who's taken my pen?'誰拿走了我的筆？ is是 'who has', because因為 'taken' is a past participle是過去分詞。

It is very common in speaking and in normal writing — messages, emails, stories, anything that is not a formal report. In a formal essay or an official document, many teachers still prefer you to write the full 'who is' or 'who has'.

It它 in speaking在口語 and in normal writing和一般書寫裡 is very common非常常見 — messages訊息, emails電子郵件, stories故事, anything that is not a formal report任何不是正式報告的東西。In a formal essay or an official document在正式作文或公文裡, many teachers很多老師 still prefer仍然偏好 you to write the full你寫完整的 'who is' or 'who has'。

Note that 'who's' can also be 'who has' as the helping verb only, not 'who has' meaning 'who owns'. We do not say 'Who's a car?' for 'Who has a car?' — for owning, we say 'Who has a car?' in full, or 'Who's got a car?' which is the helping-verb kind again.

Note留意 'who's' can also be也可以是 'who has', as the helping verb only但只限當助動詞的用法, not 'who has' meaning 'who owns'不是「誰擁有」的那種 who has。for 'Who has a car?'想問「誰有車」時 We do not say我們不說 'Who's a car?' — for owning要講擁有, we say in full我們說完整的 'Who has a car?', or或說 'Who's got a car?', which is the helping-verb kind again這又是助動詞的那一種了。