What's the difference between a dominant and a master? What do the words actually mean?
While no one can really tell anyone else what their title in BDSM really means, there are some widely accepted definitions for some words out there. For instance, there is an accepted BDSM community-wide definition for dominant and one for master.
The difference is mostly semantic, but understanding them might help some people to understand the type of partner for which they are looking or the type of relationship into which they want to place themselves. If nothing else, it will let some people know the best way to address themselves when speaking to members of their BDSM community.
Generally speaking, a dominant is a person that is willing to enter into a domestic 24/7 BDSM relationship with a submissive. A dominant's primary motivation, in most cases, is not TPE, corporal punishment, or excessive forms of bondage and sadism. A dominant enjoys the perceived power and control he has over his submissive and is focused more on the discipline, rules and control aspects of the relationship.
Different than a dominant is a master. Typically, a master want a TPE, 24/7, slavery type of relationship. He likes to exert full control over a submissive and will enjoy corporal punishment and, occasional sadism. He, too, wants power and control over his partner, but in a different way than a dominant does. A dominant is usually content to set rules and have them follwed through a routine of discipline and training. A master sets specific rules for all aspects of his partner's life, from what she will wear, to what she will eat, to how she will walk and talk in social situations. Most frequently, when someone refers to a TPE type relationship, they are going to refer to it in the sense of master and slave, not dominant and submissive.
There are other forms of 'dominant' roles in BDSM and kink, too. The sadist is one, the top is another. A sadist enjoy inflicting pain and receives sexual gratification from it. A top is a scene player, like a bottom or a switch, that enjoys occasional play and scening, but doesn't necessarily look for a 24/7 type relationship. In fact, most tops are kind of put off by the idea of living a 24/7 BDSM lifestyle. They want to play on the weekends and go to work on the weekdays. They want seperation of their lives, not constant immersion in the vanilla world or the BDSM world.
These definitions are not specific, by the way, and they are combinable. Just because you call yourself a dominant doesn't mean you won't administer corporal punishment, it just means you don't require the micromanagement of your submissive's entire life. Just because you are a sadist doesn't mean you don't enjoy the occasional topping every now and then just to see your favorite toy crawl before she gets her ass beaten.
As a rule, BDSM terms are often non-specific and blanketing. Unless you know exactly what your preferences are, I would recommend sticking to the general 'dominant' term. It's widely accepted and covers about everything, except topping. It's the term I prefer for myself.
And this doesn't even cover leather doms, daddies, spankophiles or the myriad other nomenclature given to the dominant side of BDSM lifestylers.