1.三者均可后接不定式，但 look 之后一般只限于 to be (且較少見)。

例如：

正：He seems / appears / looks to be tired. 

       他好像很累了。

正：He seems [appears] to have travelled a lot. 

       他似乎去過不少地方。

誤：He looks to have travelled a lot.

2. look, seem 之后可接介詞 like，但 appear 之后一般不能。

例如：

He looks / seems like a fool. 

他看起來像個大傻瓜。

3. appear 和 seem 不用于進行時態，但 look 有時可這樣用。

例如：

正：He looks /is looking well. 

       他看上去氣色不錯。

誤：He is seeming / appearing well.

4. 三者均可用于 it 開頭的句子，且三者之后均可接以 as if 或 as though 引導的從句，另外 appear 和 seem 之后還可接 that 引導的從句。

例如：

It looks / seems /appears as if he has lost interest in his job. 

看來他對自己的工作已失去了興趣。

It seems / appears that he is very tired. 

他似乎很累了。

注：后接 that 從句時，有時可用 so，not 代之。

例如：

A：Are they reliable? 

     他們可靠嗎?

B：It seems / appears so (not). 似乎是可靠的(不可靠)。