動詞的---ing形式有時在用法上相當于名詞，因此叫做動名詞，在句子中可以作主語、表語、賓語和定語。
一、主語
Reading is learning, but using is also learning.
Seeing is believing.
It’s interesting planning a holiday.
但是表語形容詞是important, necessary等時，只能用不定式，如：
It’s important to learn English by using it.
動名詞復合結構作主語時，邏輯主語不論是名詞還是代詞，常用屬格，如：
Her going there won’t do any harm.
It is no use Mary’s pretending that she didn’t know the rules.
二、表語(表示主語的內容)
Seeing is believing.
Our duty is serving the people heart and soul.
What she hated most was resting at home and doing nothing.
My job is teaching English.
注意：有時不定式作表語可以表示將來時，如：
We are to go to the new museum for a visit tomorrow.
區別的訣竅是表語不定式可以和主語對調，如：
Teaching English is my job.
三、賓語
1． 只接動名詞作賓語的動詞有：be used to, consider, delay,. dislike, enjoy, escape, excuse, feel like, finish, give up, cannot help, imagine, keep (on), look forward to, mind, miss, practise, put off, resist, pardon, risk, suggest, permit, allow, forbid, advise, set about等。
I can’t risk missing the train.
I don’t mind Jane/ Jane’s buying another one.
2．接動名詞和不定式作賓語都可以的動詞有：
1) 動名詞和不定式意義基本一致的動詞：like, love, hate, begin, start, continue, prefer, need, want, deserve等；
Jack loves listening / to listen to pop music.
My hair needs cutting.= My hair needs to be cut.
2) 動名詞和不定式意義有些差別的動詞：remember, forget, try, help,mean, stop, go on等。
I remember posting the letter.
I will remember to post the letter.
I’ve quite forgotten putting it there.
I forgot to put it there.
He tried to write better.
He tried writing better with a brush.
I couldn’t help finishing reading the book.
I’m sorry I can’t help finish doing the job.
Do you mean to tell me you didn’t post it?
If you didn’t do it, it will mean waiting for a long time.
They stopped talking.
They stopped to talk.
He went on pointing out mistakes in the paper.
He went on to point out mistakes in the paper.
注意：regret的用法。
He regretted missing(= having missed = to have missed) the last train.
四、定語（表示被修飾的名詞的性能或用途）
freezing point, living room, sleeping car, waiting room, dining room, writing dest, walking stick, washing machine, smoking room等。
注意：a singing bird中的singing現在分詞，表示被修飾的名詞的動作。