Professional Boxing
Professional boxing is way different from the amateur one from all possible points of view. Professional boxing is like the meaning of life for those fighters and not just a good way to keep in feet. People dedicate their whole lives for boxing and they don't want any other profession because boxing is everything for them and they can't live without it.
Professional boxing is much rougher than the amateur boxing, and it is not a wonder. First of all the common fight of professional boxing usually consists of ten or twelve rounds. Each round lasts for three minutes and there is no way for the fight of professional boxing to consist of less than ten rounds, and those round are the tough rounds.
And there are seventeen weight classes unlike the amateur boxing. But, the main peculiarity of it is that fighters are always without the additional equipment than would reduce the weight of blow. They only wear shorts and their trunks and heads are not protected with some additional equipment, there is only the thing that protects the most precious thing of every man.
It is referee who can make his decision about the physical state of a fighter. Say, in case referee sees a boxer feels not very good he may proclaim the knockdown even in case boxer says he is okay.