屬正式用詞，主要用于肯定句或疑問句，一般不用于否定句(否定句可用either)，它在句中通常放在實(shí)義動(dòng)詞之前，特殊動(dòng)詞 (動(dòng)詞be、情態(tài)動(dòng)詞、助動(dòng)詞)之后，有時(shí)也放在整個(gè)謂語前面或放在句首或句尾 (較少見，且多半是因?yàn)閺?qiáng)調(diào)之故)。

一、Also

also是用在肯定句里面，它表示的是兩個(gè)人干了同樣的事，或者兩件事是同一個(gè)人干的，also一般是位于be動(dòng)詞，助動(dòng)詞，情態(tài)動(dòng)詞的后面，但在行動(dòng)詞的前面。比如像：

He has been to Beijing. I have also been there.

He is good at English. He is also good at Japanese.

不過不也有一種特殊情況，那就是在表示強(qiáng)調(diào)的時(shí)候，also也是可以放在be動(dòng)詞，助動(dòng)詞，情態(tài)動(dòng)詞的前面。比如像：

I can also do it.

I also can do it.

二、As well

這個(gè)一般在口語中用的比較多，也是用于肯定句，和too可以進(jìn)行互換，通常是位于句末。比如像：

She not only sings,

She plays the piano as well.

三、Too

Too和as well的用法基本一樣，它比also會(huì)更加的通俗易懂，和also，as well都可以進(jìn)行相互的替換，可以放在句子的中間，也可以放在句末位置。比如像：

Xiao Li went to Beijing and Xiao Zhao, too, went to Beijing.

He studies hard and I study hard, too.

四、Either

這個(gè)與前面三個(gè)不太一樣，它是用在否定句里面的，并且還只能放在句末。比如像：

He didn't know it. I didn't know it either.

I can't speak French and can't write it, either.