三者均可用作连系动词,意为“好像”、“似乎”等,区别如下：
1.从词义上看：look 指视觉印象；appear 指外表给人的印象；这两者可能是真象也可能是假象,appear 的不确定性更大一些.seem 侧重指根据某种迹象作出的推断,也不一定是事实.
2.从句型搭配和用法上看：
(1) 三者均可后接不定式,但 look 之后一般只限于 to be (且较少见).如：
正：He seems [appears,looks] to be tired.他好像很累了.
正：He seems [appears] to have travelled a lot.他似乎去过不少地方.
误：He looks to have travelled a lot.
(2) look,seem 之后可接介词 like,但 appear 之后一般不能.如：
He looks [seems] like a fool.他看起来像个大傻瓜.
(3) appear 和 seem 不用于进行时态,但 look 有时可这样用.如：
正：He looks [is looking] well.他看上去气色不错.
误：He is seeming [appearing] well.
(4) 三者均可用于 it 开头的句子,且三者之后均可接以 as if 或 as though 引导的从句,另外 appear 和 seem 之后还可接 that 引导的从句.如：
It looks [seems,appears] as if he has lost interest in his job.看来他对自己的工作已失去了兴趣.
It seems [appears] that he is very tired.他似乎很累了.
注：后接 that 从句时,有时可用 so,not 代之.如：
A：Are they reliable?他们可靠吗?
B：It seems [appears] so (not).似乎是可靠的(不可靠).
另外,比较以下同义句型：
It seems [appears] that he is ill.＝He seems [appears] to be ill.他似乎病了.
