3.already，yet 两者均为已经之意，但already一般用于肯定句中，而yet一般用于否定句和疑问句中，如：The guests have already arrived.客人已经到了。Have the guests arrived yet?客人到了吗？The guests have not arrived yet.客人还没有到。不过，有时already也可用于疑问句中，但意义与yet不同，already用于疑问句中表示惊讶。试比较：

　　（1）Have you had lunch yet？

　　（2）Have you had your lunch already？

　　句（1）是询问信息，意为：你吃过午饭了吗？句（2）表示惊讶，意为你已经吃过午饭了？yet有时也用于肯定句中，但yet在肯定句中的意思与still相同，表示仍然、还，与already不同：Dont worry. There is yet/still time for you to prepare for the exam.不用担心，你仍然有时间去准备参加考试。The plans are yet to be approved. 计划尚待批准。或者表示（未来某一时间）迟早、早晚：He may surprise us all yet.他迟早会使我们大吃一惊的。The enemy may win yet if we relax our efforts.如果我们松劲，敌人还是迟早有可能获胜的。

　　4.also，either，too，as well四者意思相同，但在用法上有不同。Also比较正式，用于肯定句或疑问句：Her sister has also gone to town. 她妹妹（或姐姐）也上城里去了。Are you also a member of his association? 你也是这个协会的成员吗？either只用于否定句，常出现于句尾：It wont do them any good，but it wont do them any harm either. 这事于他们无补也无损。Too和as well较口语化，常可互换使用：The dog is hungry，and thirsty too/as well. 这条狗既饿又渴。区别在于too只能用于肯定句，且在句中位置灵活：We，too，are going away.我们也要离开。As well 一般只用于句末：I understood from her that you undertook other important work as well.我从她那里了解到你还干其他一些重要的活。

　　3.already，yet 两者均为已经之意，但already一般用于肯定句中，而yet一般用于否定句和疑问句中，如：The guests have already arrived.客人已经到了。Have the guests arrived yet?客人到了吗？The guests have not arrived yet.客人还没有到。不过，有时already也可用于疑问句中，但意义与yet不同，already用于疑问句中表示惊讶。试比较：

　　（1）Have you had lunch yet？

　　（2）Have you had your lunch already？

　　句（1）是询问信息，意为：你吃过午饭了吗？句（2）表示惊讶，意为你已经吃过午饭了？yet有时也用于肯定句中，但yet在肯定句中的意思与still相同，表示仍然、还，与already不同：Dont worry. There is yet/still time for you to prepare for the exam.不用担心，你仍然有时间去准备参加考试。The plans are yet to be approved. 计划尚待批准。或者表示（未来某一时间）迟早、早晚：He may surprise us all yet.他迟早会使我们大吃一惊的。The enemy may win yet if we relax our efforts.如果我们松劲，敌人还是迟早有可能获胜的。

　　4.also，either，too，as well四者意思相同，但在用法上有不同。Also比较正式，用于肯定句或疑问句：Her sister has also gone to town. 她妹妹（或姐姐）也上城里去了。Are you also a member of his association? 你也是这个协会的成员吗？either只用于否定句，常出现于句尾：It wont do them any good，but it wont do them any harm either. 这事于他们无补也无损。Too和as well较口语化，常可互换使用：The dog is hungry，and thirsty too/as well. 这条狗既饿又渴。区别在于too只能用于肯定句，且在句中位置灵活：We，too，are going away.我们也要离开。As well 一般只用于句末：I understood from her that you undertook other important work as well.我从她那里了解到你还干其他一些重要的活。