英语里除了现在进行时,为什么有的词还是ing形式?

2.一些特殊表达..如:be good at doing sth
enjoy doing sth.
be busy doing
feel like doing
thank you for doing
do some cooking/cleaning/reading/shopping/washing
go swimming/fishing/shopping/skating/boating
二．动词现在分词由动词原形在词尾加ing构成,其规则如下：
1）一般情况下直接加ing think---thinking sleep---sleeping
study---studying speak---speaking
carry---carrying say---saying
2）以不发音的字母e结尾的单词,去掉字母e,再加ing
wake---waking make---making come---coming
take---taking leave---leaving have---having
3）以重读闭音节结尾,呈现“辅,元,辅”结构的动词,先双写末尾的辅音字母,再加ing .初中学过的这类词有：begin,cut,get,hit,run,set,sit,spit,stop,swim,beg,drop,fit,nod,dig,forget,regret,rid,等.(visit 不是以重读闭音节结尾,不用双写)
travel虽然重读第一音节,词尾音节不重读,但是现在分词仍要双写末尾辅音字母,然后再加ing ,如：travel---travelling.初中阶段此类词只有这一个.
4）以 y 结尾的动词 直接加 ing
carry—— carrying enjoy—— enjoying
5）以ie结尾的动词,把ie改为y ,再加ing
die---dying lie---lying
要特别注意有些动词没有进行时态.
1、表示状态、思想、感情和感觉的动词,如：see,hear,love,know,want,hope,think等,没有进行时态.
2、当have/has作为“拥有”时,没有进行时态,但表示“开会,吃饭,玩得高兴”等意思时,可以用进行时表达.I am having many books.（这是错误的句子）
I am having a good time.（这才是正确的句子）
be动词(is.am.are).介词后面加ing形式.还有固定的词组搭配要记住
某些动词后出现非限定性动词时只能用动名词作宾语,不能用不定式.常见的此类动词有：advise,allow,permit,avoid,consider,enjoy,finish,give up,cannot help,imagine,include,keep,keep on,mind,miss,put off,delay,practise,resist,suggest,depend on,think about,set about,succeed in,worry about,burst out,insist on,can’t stand,be used to,get used to,devote…to…,look forward to,pay attention to,get down to等.如：
They went on walking and never stopped talking.他们继续走,说个不停.
I found it pleasant walking along the seashore.在海滩上走真是乐事.
（2）作介词的宾语
We are thinking of making a new plan for the next term.我们正考虑为下学期制定新的计划.
Shall we have a rest or get down to doing our work?我们休息呢还是开始干活?
（3）作形容词的宾语
The music is well worth listening to more than once.这种曲子很值得多听几遍.
We are busy preparing for the coming sports meet.我们正为马上到来的运动会忙着做准备.
3、作表语
动名词作表语时句子主语常是表示无生命的事物的名词或what引导的名词性从句.表语动名词与主语通常是对等的关系,表示主语的内容,主语、表语可互换位置.
Your task is cleaning the windows.你的任务就是擦窗户.(Cleaning the windows is your task.)
What I hate most is being laughed at.我最痛恨的就是被别人嘲笑.(Being laughed at is what I hate most.)
4、作定语
动名词作定语往往表示被修饰词的某种用途.如：
a walking stick ＝a stick for walking=a stick which is used for walking
a washing machine=a machine for washing=a machine which is used for washing
a reading room=a room for reading=a room which is used for reading
a measuring tape=a tape for measuring=a tape which is used for measuring
sleeping pills=pills for sleeping=pills which is used for sleeping