Is it possible to put have sub-categories like the following example:

Category #1 -> Subcategory #1
Category #2 -> Subcategory #1

What I mean by that is I would like to have two parent categories, and inside each parent, I would like to have a copy of the same subcategory in each parent, or do I have to create separate categories for each parent?

A better understanding would be this:

Employment Listing Type

Help Wanted
Help Offered

I would like to put all my current categories in both help wanted and help offered is that possible or do I have to create the same categories again, with different keys?