Which + noun?
Which book do you want?
你想要哪本书？
哪个；哪些；无论哪个
任何一个；无论哪些。；哪一个；那一个
the ones that; whichever
任何一个；无论哪些。
The/Any ones that; whichever.
The shop sells three kinds of apples, and customers can choose which they want.
这家商店卖三种苹果，顾客可以挑他们要哪些。
用法提示：which 作代词，指代可选择的物品（哪些/哪一个）。
There are two routes to the station; please tell me which is faster.
去车站有两条路线；请告诉我哪一条更快。
用法提示：which 作代词，在问句中指代两个选项中的某一个。
All the shirts look nice, but I can't decide which to buy.
所有衬衫看起来都很好，但我拿不定主意买哪一件。
用法提示：which 作代词，与不定式搭配，表示“哪一件”。
Which book do you want?
你想要哪本书？
常用于选择范围明确的情形。
Which of these options is best?
这些选项中哪个最好？
非限制性定语从句中，which指代先行词。
The car, which was red, belonged to John.
那辆红色的汽车是约翰的。
限制性定语从句中，which指代先行词，有时可省略。
The book which I read was interesting.
我读的那本书很有趣。
与which均可表示“任一”，但whichever更强调选择不受限制，常用于让步或条件句中。
在限定性定语从句中可替代which；但that不能用于非限定性从句，也不能直接放在介词后。
grammar · medium
易错句子Which is it possible?
正确表达Is it possible?
“which” 用于提供选项的疑问句，而一般疑问句应使用助动词置于句首。
grammar · medium
易错句子Which is your job?
正确表达What is your job?
当询问不限定范围的信息时，用“what”而非“which”，因为“which”暗示有限选项。
which（代词）用于在确定的、有限的范围中选择“哪个/哪些”；what 用于开放式提问，不预设选择范围。
在限制性定语从句中，that 和 which 都可指物；但 which 还可用于非限制性定语从句（逗号后），that 不能。
which 与 witch 同音（/wɪtʃ/），但 which 是代词，意为“哪个/哪些”；witch 是名词，意为“女巫”，拼写和词性完全不同。
（……中的）哪一个/哪些
Which of these books is yours?
这些书中哪一本是你的？
哪一个
I can't decide which one to choose.
我无法决定选哪一个。
哪个是哪个
The twins look so alike that I can't tell which is which.
这对双胞胎长得太像了，我分不清哪个是哪个。
在其中
This is the room in which we met.
这是我们见面的房间。
其中
She has three cats, one of which is black.
她有三只猫，其中一只是黑色的。
所有这些
He passed the exams, all of which were difficult.
他通过了所有考试，这些考试都很难。
pronoun
which 常用于询问在多个选项中做选择，choice 表示被选中的对象或行为。
which 常与 option 搭配构成 which option，指可供选择的事物。
在需要从几个备选中确定一个时，which 用于提问，alternative 表示其中一个备选。
which 常与 among 连用，表示从一组事物中选出一个。
which 引导的问句常询问偏好，prefer 表达选择时的倾向。
哪个是哪个；谁是谁（用于表示无法区分两个相似的人或物）
The twins look so alike that I can never tell which is which.
这对双胞胎长得太像了，我永远分不清哪个是哪个。
如果是那样的话；在这种情况下
He might be stuck in traffic, in which case we should wait a little longer.
他可能堵在路上了，如果是那样的话，我们该多等一会儿。
你站在哪一边？
From the American folk song 'Which Side Are You On?', written by Florence Reece in 1931 during a coal miners' strike. It has been adapted by civil rights, labor, and protest movements worldwide, and remains a powerful call to take a stance.
出自美国民谣歌曲《Which Side Are You On?》，由弗洛伦斯·里斯于1931年在煤矿工人罢工期间创作。该曲被民权、劳工和全球抗议运动广泛改编，至今仍是号召人们表态的有力口号。
先有鸡还是先有蛋？
A famous philosophical riddle used to describe unresolvable causal dilemmas. It appears in comedy, science discussions, and pop culture as a shorthand for two things that depend on each other.
一个著名的哲学谜题，用来形容无法解决的因果难题。在喜剧、科学讨论和流行文化中常用来代表两件互相依赖、无法分出先后的事物。
Dictionary facts from DICTIONARY_API_DEV, ECDICT, WIKTIONARY.