Prince is the most common title for the ruling (or otherwise most powerful) vampire of a domain. Kindred use Prince in its original generic sense, stemming from Roman law, meaning any ruling monarch. (Machiavelli's The Prince also uses this meaning.) The term is gender neutral and is used for a ruler of either sex. Prince is a traditional but not always official title: many ruling Kindred use others, including Cardinal, Lord, Sultan and so on. Very few call themselves Kings, however.
The nature and extent of a Prince's authority can vary greatly from one domain to another, but typically a Prince is an autocrat, and almost always one of the elders of their domain. They usually achieve their position through political, martial or social ability, though rarely a Prince may be appointed or, as in some Carthian domains, elected, but this is uncommon. In any case, most Princes rule as dictators in order to keep the Kindred of their domains under control and enforce whatever laws they see fit; these usually include at least the three Traditions, though again they vary grearly depending on the beliefs of the individual Prince.