have和having的区别和用法

ave是动词原型主要用在一般现在时中，或者用在助动词和情态动词之后。having可以用在现在进行时和一般将来时中，一般在系动词或介词之后

The two groups of children have quite different characteristics.

这两组儿童具有截然不同的特点。

Now she won't have to go out to work any more.

现在她不必再出去工作了。

I'm having treatment for my back problem.

我正接受背部疾患的治疗。

Few people can count on having a job for life.

几乎没有人能指望一辈子都干一个工作。