人
地方
事物
所有
everyone
everybody
everywhere
everything
部分（肯定）
someone
somebody
somewhere
something
部分（否定）
anyone
anybody
anywhere
anything
无
no one
nobody
nowhere
nothing
以 some 和 any 开头的不定代词描述不定丶不完整的量，就如单独使用 some 和 any 的方式一样。
不定代词在句中的位置跟名词一样。
名词
不定代词
I would like to go to Paris this summer.
I would like to go somewhere this summer.
Jim gave me this book.
Someone gave me this book.
I won't tell your secret to Sam.
I won't tell your secret to anyone.
I bought my school supplies at the mall.
I bought everything at the mall.
肯定句
在肯定句中，以 some 开头的不定代词描述的是不定的量。以 every 开头的不定代词是描述完整的量。而以 no 开头的不定代词则是描述不存在丶不在场的人或事物；通常会用在具有否定意思的肯定句，但这类句子并不是否定句，毕竟句中没有 not 这个字。
例句
Everyone is sleeping in my bed.
Someone is sleeping in my bed.
No one is sleeping in my bed.
I gave everything to Sally.
He saw something in the garden.
There is nothing to eat.
I looked everywhere for my keys.
Keith is looking for somewhere to live.
There is nowhere as beautiful as Paris.
以 any 开头的不定代词可以用在肯定句，跟 every 的意思很接近：任何人丶任何地方丶任何事物。
例句
They can choose anything from the menu.
You may invite anybody you want to your birthday party.
We can go anywhere you'd like this summer.
He would give anything to get into Oxford.
Fido would follow you anywhere.
否定句
否定句只能用 any 开头的不定代词。
例句
I don't have anything to eat.
She didn't go anywhere last week.
I can't find anyone to come with me.
在很多情况下，当句中含有 any 开头的不定代词，只要将原先的不定代词改为以 no 开头的不定代词，就可以变成带有否定意义的肯定句。不过这样的改写会改变句子的意思。句中若含有 no 开头的不定代词，语气会变得更强烈，而且会传达出防卫丶绝望丶愤怒等情绪。
举例
I don't know anything about it. = 中立
I know nothing about it. = 防卫
I don't have anybody to talk to. = 中立
I have nobody to talk to. = 绝望
There wasn't anything we could do. = 中立
There was nothing we could do. = 防卫/愤怒
否定问句
以 every丶some丶和 any 开头的不定代词可以用在否定问句上，这类问句一般可以用 Yes/No 来回答。
以 any 和 every 开头的不定代词会被用在 Yes/No 问句上；而以 some 开头的不定代词，会透露出我们已知道该问题的答案丶或对答案有所怀疑。
例句
Is there anything to eat?
Did you go anywhere last night?
Is everyone here?
Have you looked everywhere?
只要在问句加上否定的缩写 n't，即成为反问句。当说话的人丢出这样类型的问句，其实是想得到否定的答案。
例句
Isn't there anything to eat?
Didn't you go anywhere last night?
Isn't everyone here?
Haven't you looked everywhere?
以 some 开头的代词只用在问句上。通常我们会知道问句的答案，或者不会得到 Yes/No 的回答（例如在提出邀请丶要求等），问这类问题的人，通常会想得到肯定的回答。
例句
Are you looking for someone?
Have you lost something?
Are you going somewhere?
Could somebody help me, please? = 要求
Would you like to go somewhere this weekend? = 邀请
如果这些问句被改为反问句，语气就会变得更绝对。在这种情况下，发问者百分之百确认他会得到肯定的回答。
例句
Aren't you looking for someone?
Haven't you lost something?
Aren't you going somewhere?
Couldn't somebody help me, please?
Wouldn't you like to go somewhere this weekend?