一、概說
連系動詞是表示不完全謂語關系的動詞，它與其后的表語一起構成謂語。常見的連系動詞有be(是)，become(成為)，get(變成)，remain(還是)，seem(似乎是)，look(看上去)，feel(感覺)等。連系動詞后的表語通常是名詞和形容詞，有時也可以是代詞、數詞、副詞、介詞短語、不定式、動名詞、從句等：
His English is excellent. 他的英語很棒。(跟形容詞)
He is a famous poet. 他是著名詩人。(跟名詞)
Money isn’t everything．金錢不是一切。(跟代詞)
She was the first to arrive．她是第一個到達的人。(跟數詞)
Who is upstairs? 誰在樓上？(跟副詞)
He is with his friends. 他和朋友在一起。(跟介詞短語)
He seems to be ill. 他似乎病了。(跟不定式)
Seeing is believing. 眼見為實。(跟動名詞)
This is what you need. 這就是你需要的。(跟從句)
二、學習連系動詞應注意的兩點
1. 關于連系動詞后接副詞作表語
連系動詞后通常可接形容詞作表語，一般不接副詞：
誤：His English is very well. 他的英語很好。(可將well改為good)
誤：Be carefully. 小心點。(應將carefully改為careful)
誤：The soup tastes nicely. 這湯味道不錯。(應將nicely改為nice)
但是，有時連系動詞后也可接副詞作表語，不過這主要限于in, on, off, out, away, behind, up, down, over, through, around, round, below, inside, outside 等少數副詞小品詞以及here, there, upstairs, downstairs等少數表示地點或方位的副詞：
Mother wasn’t in last night. 母親昨晚不在家。
The meeting was over at five. 會議五點結束。
Come along. The taxi is outside. 來吧，出租車在外面。
Mother is downstairs waiting for you. 母親在樓下等你。
2. 關于連系動詞后接不定式
(1) 連系動詞be后根據情況可自由地接不定式作表語：
My dream is to be a scientist. 我的夢想是當一名科學家。
All I could do was to wait. 我只能等。
My plan was to go from London to Paris. 我計劃從倫敦去巴黎。
I was to have seen Mr Kay. 我本要去見凱先生的。
(2) seem, appear, prove, continue, turn out, get, grow, come 等連系動詞后也可接不定式(尤其是to be)作表語：
She always seems to be sad. 她常常顯得很憂傷。
My advice proved to be wrong. 我的意見證明是錯的。
She appears to have many friends. 他好像有很多朋友。
The weather turned out to be fine. 天氣結果很好。
Circumstances continue to be favorable. 情況仍然是有利的。
He has grown to like studying English. 他漸漸喜歡學英語了。
【注】若所接不定式為to be，通常可以省略。不過，若其后接的是表語形容詞，則to be通常不宜省略。另外，連系動詞look后能否接to be似乎尚有爭論，不過，在現代英語中接to be的現象已較普遍。
(3) sound, smell, feel, taste, become等連系動詞后通常不能接不定式：
誤：These oranges taste to be good. (應去掉to be)
誤：The roses smell nice. (應去掉to be)
(4) 有的連系動詞后接的從句可用不定式來改寫：
It seems that that she’s right. / She seems to be right. 她似乎是對的。
It appears that you have made a mistake. / You appear to have made a mistake. 似乎你弄錯了。
