以下摘自朗文当代英语词典 供你参考：
WORD CHOICE:as,like,as if
Use AS in comparisons in the expression as ...as ,with an adjective or adverb in between :Basketball is as popular as football here.| He can't read as well as his classmates .
AS is also used in the expressions not so .as and the same (...) as :I wouldn't go so far as that.| He is the same age as me.
Use LIKE in comparisons followed by a noun :A movie is not like a book (NOT not as a book).|Like other people (NOT as other people),he values his privacy.
Use AS IF followed by a clause to compare a real situation with an imaginary situation :He talked to them as if they were children.
!Some people use like in this sort of comparison :They act like they own the place.It is better not to do this as many people think it is incorrect.
!as if cannot be followed directly by a noun :You treat them as if they were your parents (NOT as if your parents).
