因此，对于没有传真号码的人而言，就不需要定义传真的值，而对于有传真号码的人，则根据他们的意愿定义该值。

So the person without a fax number does not need to define a fax value, whereas the person with a fax number is free to do so as they please.

youdao

例如，一个人可能有传真号码，而另一个人没有。

For example, one person may have a fax number, while another may not.

youdao

这就像电话或者传真号码，我们不能没有。

It's just like a telephone or fax number which we cannot do without.

youdao