连词有：as, as if/ as though
(1) as引导的方式状语从句, 意为"以……方式;如同……那样"，从句有时是省略句。如：
Do as I say. 要照我说的做。
I did just as you told me. 我正是照你说的办的。
Air is to man as water is to fish. 空气之于人犹如水之于鱼。
(2) as if/as though引导的方式状语从句
as if和as though的用法相同，都作"好像，仿佛"解。如：
二者引导的状语从句往往用虚拟语气，表示与事实相反。as if比as though更为常用。但也可用陈述语气，表示所说的情况是事实或实现的可能性较大。如：
They looked at me as if , as though I were mad.
They look as if/as though they know each other.