I feel dumb for having been a web programmer for so long and not knowing the answer to this question, I actually hope it\'s possible and I just didn\'t know about rather tha
Less and Sass are CSS pre-processors which extend CSS language in valuable ways. Just one of many improvements they offer is just the option you're looking for. There are some very good answers with Less and I will add Sass solution.
Sass has extend option which allows one class to be fully extended to another one. More about extend you can read in this article