From ArticleWorld

The title of prince can be conferred in a number of ways. In the most obvious cases, a prince is the male offspring of a ruling monarch and first in line for the throne. He may be a member of the royal family and again in line for the throne but further down the line. The husband of a reigning queen may also be referred to as a prince.

European systems

In Italy, a prince is inferior to a duke whereas in Spain he is always of royal blood. Throughout history, other definitions of prince have come to be accepted depending on the country and the time. Translation also plays a part when ‘prince’ is used for want of a better word. E.g. When referring to a person of nobility or an aristocrat in a non-English speaking country who has no connection to a royal family.

The title of prince depends not only of heritage but can also be used as a courtesy title. Heads of states of principalities or micronations – self styled nations, usually very small – may take the title, in some cases self-bestowed. A head of a feudal state may also have been granted the title.

The term is also used in religion with Prince of the Church referring to Roman Catholic Cardinals, who are treated in the same way as those of royal blood in protocol.

Non-Western concepts

The title is not only a Western concept, however. Sheikhs and Sultans have princely connotations and in ancient China, there were 5 grades of princes at one time.

The term can also be applied in a more general way to refer to someone of high regard or simply a man who is generous or particularly chivalrous. Prince charming, for example, may not be of royal or noble blood at all.