一、文法不同
as if 引导的方式状语从句或表语从句,用虚拟语气。
例句: He acts as if he knew me. 他显得认识我似的。
as though 表示与现在事实相反,谓语动词,用would (might, could)+动词原形。
例句:They treat me as though I were a stranger. 他们待我如陌生人。
二、时态不同
as if 表示与过去事实相反,用过去完成时。
例句:This meat tastes as if it has already gone bad. 这肉吃起来似乎已经坏了。
as though 表示将来的可能性不大,用一般过去时。
例句:I feel as though I’m floating on air. 他感到好像漂浮在空中。
三、语境不同
as if 用来描述比较悲惨的境遇或者状况。
例句:It is not as if he were poor. 他不像穷的样子(或他又不穷)。
as though 语境属于中性,可以用到很多情境中。
例句:It is not as though you were going away for good. 又不是你离开不回来了。