if
1.if 作為"是否"的意思時,常用在口語當(dāng)中,引導(dǎo)疑問從句,如 DO do you know if xiaoli is at home?你知道小李是否在家嗎?
2．作為”假如”的意思時,引導(dǎo)的是條件從句,用于虛擬語氣當(dāng)中,如；If it should be necessary,i could come at six.假如有必要的話,我可以六點鐘來
as if 是似是而非[像什么似的（但其實不是）]的意思.
eg.
As if i did it!
就像是我做了一樣!