相当于名词,在句中可以作主语、宾语和表语,但不能作定语
There is someone outside the door.(主语)
I don't have anything to say today(宾语)
Money isn't everything.(表语)
被形容词、动词不定式等修饰时,形容词和动词不定式等应置于其后
I have something important to tell you.
Do you want anything to read?
作主语时表示单数概念,谓语动词用单数形式
Everything begins to grow in spring.
some-不定代词通常用于肯定句中;any-不定代词则多用于否定句或疑问句中。但在表示请求、建议等的疑问句中,问话者希望得到肯定答复时,常用含有some-的不定代词,如something,somebody,someone等
Will you ask someone to carry the box for me?
Would you like something to drink?
anyone, anything也可用在肯定句中,前者表示“任何人”,后者表示“任何事”