英语中所谓的补足语,就是用来补充说明宾语、或主语的句子成分.
例如：
(1) I saw him playing basketball yesterday.
Playing是宾语him的补足语.
(2) He was seen playing basketball yesterday.
Playing变成了主语He的补足语.
英语中主语补足语的形式是比较多样,归纳起来,常见的有以下几种：
名词、形容词、副词、动词、介词短语等.
1.as后面接名词、形容词、分词等用作主语补足语.例如：
① English is taken as a useful means for research work.(n)
2.（We take English as a useful means for research work.）
② The news is considered as true.(adj)
（The villagers considered the news true.）
③ The stool is usually thought as having four legs
(We think the tool as having four legs.)
④ The vase is thought as broken.(p.p)
(The customers think the vase broken)
⑤ The books in the study must be kept in good order.(prep.phrase)
(Readers must keep the books in good order after reading them.)
⑥ He was found in good health.(prep.phrase)
(We found him in good health.)
⑦ English is considered of great importance for us.
(We consider English of great importance.)
3.可以带主补（宾补）结构的动词有：
(1) 动词elect,call,name,make,find,leave等.后面常接名词或名词短语作补语.例如：
① The dog is called Karl.（The dog is Karl.）
② Coal is sometimes called stored-up sunlight.(Coal is stored-up sunlight.)
③ He was found the right man for the job.(He was the right man for the job.)
(2) 动词keep,make,paint,cut,burn,beat,wash,find,consider,wipe等,后面常接形容词用作主语补足语.例如：
① The door was painted white.（We painted the door white.）
② The old man was found weak.(We found the old man weak.)
③ The classroom is always kept clean every day.(The students always keep the classroom clean every day.)
(3) 感官动词see,watch,hear,feel,listen to,look at,imagine等,后面接分词或分词短语用作主语补足语.例如：
① He is often heard reading English.（His classmates often hear him reading English.）
② The professor was seen making an experiment in the chemistry lab.(The students saw the professor making an experiment in the chemistry lab.)
③ The glass was found broken.(He found the glass broken.)
④ The classroom was found crowded with people.(We found the classroom crowded with people.)
