also用语句中.I also like English.
too 用于句末.I like English,too.
either只用于否定句.I don't like English,either.
as well(as)用于肯定句的句末.I like English as well.
I like Englishas well as math.=I like English,and I like math as well.
一、as well 用法：

1、as well常用作状语,作“又；也”解,相当于too或also,常位于句末,无须用逗号与句子分开.如：

I am going to London and my sister is going as well（＝going,too）.
我要到伦敦去,我妹妹也要去.

I not only play the guitar,I sing as well（＝I also sing ）.
我不但弹吉他,而且还演唱.

2、as well 在口语中也可用于句中,作“也好,也行”或“倒不如”解,用来缓和语气.如：

You may as well go、
你去也好.

The weather was so bad that we might（just）as well have stayed at home.
天气太坏了,早知道如此,倒不如呆在家里为好.

3、as well 可以直接用于just后,用作应答语（可视为It's just as well、的省略）,作“幸亏,幸而；无妨；没关系”解.如：

—We were too late to see the film.
我们去得太晚了,没有看上电影.

—Just as well、I hear it isn't very good.
不必遗憾,我听说电影也不怎么样.

二、as well as 用法

1、as well as常用来连接两个并列的成分,作“也,还”解.它强调的是前一项,后一项只是顺便提及.因此连接并列主语时,谓语动词与前一项一致；而用not only ...but also...连接时,谓语动词与后一项一致.如：

Your wife as well as you is friendly to me.
不仅你而且你的妻子也对我很友好.
（＝Not only you but also your wife is friendly to me、）

Electric energy can be changed into light energy as well as into sound energy.
电能既可以被转变成声能,又可以被转变成光能.

2、as well as 用来表示同级比较,指“一样好”.如：

You look as well as you did ten years ago.
你的身体看起来还和十年前一样好.

He plays the guitar as well as you.
他的吉他弹得和你一样好. also用语句中.I also like English.
too 用于句末.I like English,too.
either只用于否定句.I don't like English,either.
as well(as)用于肯定句的句末.I like English as well.
I like Englishas well as math.=I like English,and I like math as well.
一、as well 用法：

1、as well常用作状语,作“又；也”解,相当于too或also,常位于句末,无须用逗号与句子分开.如：

I am going to London and my sister is going as well（＝going,too）.
我要到伦敦去,我妹妹也要去.

I not only play the guitar,I sing as well（＝I also sing ）.
我不但弹吉他,而且还演唱.

2、as well 在口语中也可用于句中,作“也好,也行”或“倒不如”解,用来缓和语气.如：

You may as well go、
你去也好.

The weather was so bad that we might（just）as well have stayed at home.
天气太坏了,早知道如此,倒不如呆在家里为好.

3、as well 可以直接用于just后,用作应答语（可视为It's just as well、的省略）,作“幸亏,幸而；无妨；没关系”解.如：

—We were too late to see the film.
我们去得太晚了,没有看上电影.

—Just as well、I hear it isn't very good.
不必遗憾,我听说电影也不怎么样.

二、as well as 用法

1、as well as常用来连接两个并列的成分,作“也,还”解.它强调的是前一项,后一项只是顺便提及.因此连接并列主语时,谓语动词与前一项一致；而用not only ...but also...连接时,谓语动词与后一项一致.如：

Your wife as well as you is friendly to me.
不仅你而且你的妻子也对我很友好.
（＝Not only you but also your wife is friendly to me、）

Electric energy can be changed into light energy as well as into sound energy.
电能既可以被转变成声能,又可以被转变成光能.

2、as well as 用来表示同级比较,指“一样好”.如：

You look as well as you did ten years ago.
你的身体看起来还和十年前一样好.

He plays the guitar as well as you.
他的吉他弹得和你一样好.