1. 這三個(gè)詞都用來談?wù)搩烧撸篵oth 意為“(兩者)都”，either意為“(兩者中)任意一個(gè)”，neither 意為“(兩者)都不”。若要指三者或三者以上，分別用 all 意為“(三者)都”，any 意為“(三者中)任何一個(gè)”，none 意為“(三者)都不”等。比較：

He has two sons; both of them are clever.

He has three sons; all of them are clever.

He has two sons; either of them is clever.

He has three sons; any of them is clever.

He has two sons; neither of them is clever.

He has three sons; none of them are clever.

2. 它們既可用作代詞，也可用作形容詞。用作形容詞時(shí)，both 后接復(fù)數(shù)名詞，而 either 和 neither 之后要接單數(shù)可數(shù)名詞。如：

Both of the brothers are here. / Both brothers are here. 兄弟倆都在這兒。

Either of the books will do. / Either book will do. 兩本書中哪一本都行。

Neither of the stories is interesting. /Neither story isinteresting. 兩個(gè)故事都沒有趣。

【注】代詞 both, either, neither 用作主語時(shí)，both 之后的謂語動(dòng)詞總是復(fù)數(shù)，either 和 neither 后的謂語動(dòng)詞通常用單數(shù)。

3. 這三個(gè)詞都可用作連詞，但搭配和意義各不相同。總的說來，要注意它們應(yīng)連接兩個(gè)平行對(duì)等的句子成分(即同為兩個(gè)主語、謂語、賓語、狀語等)：

(1) both……and……表示兩者兼有。如：

She was both tired and hungry. 她又累又餓。

He speaks both English and French. 他既說英語又說法語。

(2) either……or……表示兩者或兩種可能性中任擇其一。如：

He must be either mad or drunk. 他不是瘋了就是醉了。

You can either write or phone to request a copy. 你可以寫信可打電話來索取一本。

(3) neither……nor……表示兩者都否定。如：

It’s neither cold nor hot. 天氣既不冷也不熱。

He neither knows or cares what happened. 他對(duì)所發(fā)生的事既不知道也不關(guān)心。

【注】以上連詞連接主語時(shí)，both……and……一般只與復(fù)數(shù)謂語連用，either……or……和 neither……nor……則通常根據(jù)就近原則，要求謂語動(dòng)詞與最鄰近主語的人稱、數(shù)保持一致。如：

Either you or I am wrong. 不是你錯(cuò)就是我錯(cuò)。

Neither he nor she was at home. 他和她都不在家。

3. 注意下面兩個(gè)同義句：

兩邊都有商店。

正：There are shops on both sides.

正：There are shops on either side.

兩個(gè)我都不要。

正：I want neither of them.

正：I don’t want either of them.