英语中什么时候用加ingTom thinks playing basketball.为什么加ing?还有像Thanks for helping me什么的，对了关于分词也说说吧。这么少分回答这么多问题，真是不好意思啊。

Tom thinks playing basketball .
中的palying basketball 是动名词作定语 因为是定语所以加ing

动词的-ing形式是动词的一种非谓语形式,由动词原形加-ing构成,包括-ing分词和-ing动名词.可以在句子中用作主语、表语、宾语、宾语补语、状语和定语.
一、作主语
1．一般形式
Seeing is believing.
眼见为信.
Coming to Hangzhou by train tkes about 16 hours.
乘火车到杭州要16个小时.
2．通常为了避免句子主语过于冗长,用it作形式主语.如：
It’s nice talking with you.
和你谈话很高兴.
It’s no use arguing with him.
跟他争论没用.
3. “There + be + no + -ing”结构,此结构的意义相当于“It’s impossible + 不定式”. 如：
There is no harm in doing so.
这样做没有害处.
二、作表语
动词-ing可用来作表语.如：
This food smells inviting.
这种食物香味怡人.
My favorite sport is swimming.
我最喜欢的运动是游泳.
Their job is cleaning the window.
他们的工作是打扫窗子.
三、作宾语
1．动词-ing形式可以用作动词、短语动词和介词的宾语
I warned her against driving fast.
Jim dislikes eating chocolate.
2．有些动词和动词短语后接宾语的非限定性动词时只能是-ing分词,常见的这类动词有：admit, acknowledge, advise, appreciate, avoid, delay, deny, dislike, enjoy, excuse, escape, fancy, finish, forgive, face, endure, involve, give up, imagine, mention, mind, miss, pardon, practise, require, resent, resist, suggest, recall, resist, understand等.
The doctor advised taking more exercise.
医生建议多锻炼.
I suggest doing it in a different way.
我建议用不同的方法做.
3.大部分“动词+介词“短词动词,只能后接动词-ing作宾语.这些动词短语有：think of, give up, aim at, put off, insist on, persist in, be good at, do well in, can’t help, keep on, leave off, feel like, be tired (afraid, capable, fond) of, set about等.
以下为to作介词的短语有：be used to, object to, devote oneself to, stick to, respond to, look forward to, see to, submit to, adapt to, apply to, accede to, get to, prefer to, adjust to, owe to, react to等.
Do you feel like having a drink?
你想喝点饮料吗?
I prefer swimming to playing basketball.
我喜欢游泳胜于打篮球.
4．有些动词既可能带-ing分词作宾语,也可以带to不定式作宾语,但在语义上却有很大的差别.如：
（1）chance to do 碰巧去做某事
chance doing 冒险试一试做某事
（2）forget to do 忘记要去做某事
forget doing 忘记曾做过某事
（3）go on to do 接着又做另一件事
go on doing 继续做同一件事
（4）remember to do 记得要去做某事
remember doing 记得曾做过某事
（5）stop to do 停下来去做某事
stop doing 停止做某事
（6）try to do 努力做某事
try doing 试一试做某事
（7）regret to do 对将要做的事表示遗憾
regret doing 对做过的事表示遗憾
（8）mean to do 打算/想做某事
mean doing 意味着/意思是做某事
四、作宾语补语
I found the parade quite interesting to watch.
这种用法通常用在下列几类动词中,后接宾语然后加上-ing 分词,构成复合宾语结构,-ing分词充当宾补成分.
1．表示感觉和心理状态的动词,如：see, hear, feel, find, smell, watch, find, listen to, look at, notice, observe等.如：
There we found him watching TV.
我们发现他在那儿看电视.
I heard someone knocking at the door.
我听见有人在敲门.
2.在有些动词（如：regard, describe, accept, think of, quote等）之后,可由as引出-ing分词词组作宾补.如：
They regarded the contract as being invalid.
他们认为合同无效.
They described the child as being very clever.
他们描述这孩子非常聪明.
3.使役动词,如：set, keep, have, get, leave, catch等.如：
Can you get my watch going again?
你能使我的表再走起来吗?
This sets me thinking.
这使我思考.
五、作状语
-ing分词作状语表示在进行一动作的同时所进行的另一动作,它对谓语动词起修饰和陪衬的作用.分词作状语可以表示时间、原因、条件、让步、结果、方式或伴随情况.
Having cleaned the rooms we began to weed the garden. (时间)
打扫完房间,我们开始在花园里除草.
Coming into the room, she saw everybody already at their work. (时间)
进屋以后,她看到人人都在工作.
Being ill, he couldn’t go to school. (原因)
因为生病,他不能去上学.
Having no interest in the topic, he didn’t go to the lecture. (原因)
由于对这个话题没有兴趣,他没去参加讲座.
Working diligently, you will certainly succeed. (条件)
只要刻苦学习,你会成功的.
Using atomic energy, we can build spaceships. (条件)
利用原子能,我们能够建造太空船.
Granting the achievements to be great, there is still something to bi desired. (让步)
(尽管)成绩是巨大的,（但）仍有一些要求改进的东西.
My car was caught in a traffic jam, thus causing the delay. (结果)
我的车被交通拥挤堵住,所以延误了.
Traveling by train, we visited a number of cities. (方式)
我们坐火车访问了好多城市.
Mary sat by the window of the classroom, reading a book. ( 伴随)
玛丽坐在教室的窗户旁,正在读一本书.
六、作定语
分词作定语时和形容词的功能是相似的.-ing分词可以单独作定语,如：
a smiling face 笑脸
a leading figure *物
-ing分词还能构成合成词作定语,如：
easy-going man 好说话的人
当分词短语做后置定语时,可以转换成定语从句.
She went on board the train leaving for Shanghai.
=She went on board the train, which was leaving for Shanghai.
她乘坐了去上海的火车.
There are two roads before us, one leading to the beach, the other to the park.
=There are two roads before us, one which leads to the beach, the other to the park.
在我们面前有两条路,一条通向沙滩,另一条通向公园.