Princes of principalities

Princes of principalities

Other princes (or the same, see below) derive their title not from their dynastic position as such (which must often be shared with brothers, etc), but from their claim to a unique title of formal princely rank, one named after a specific principality, not after the suzerain/sovereign state, even if they belong to one.
Princes as ruling MonarchsA prince or princess who is the head of state in a monarchy is a reigning prince, which had no other specific, formal (rank) title, and their domain, typically smaller than a kingdom, is called a "principality".
This can be a regular nation, even sovereign, but his protocolary ranking is below a grand duke.
Example: Prince Albert II of the principality of Monaco. In the same tradition/vein some micronation 'monarchs' establish themselves as (usually merely nominal) 'princes'.
Example: Prince Roy of Sealand The term "prince" has also been used to describe, in languages like English that lack a specific word for this concept, the head of a feudal (vassal) state of lower rank; for example, it has been used as a synonym for duke at times.
In German, such a prince is also called "Fürst" (capital obligatory in German grammar), and there are equivalents in most languages in the tradition of the Holy Roman Empire, where these abounded.
Princes tasting the throneVarious monarchies provide for different modes in which princes of the dynasty can temporarily of permanently share in the style and/or office of the Monarch, e.g. as Regent of Viceroy (though these offices must not be reserved for members of the ruling dynasty, in some traditions they are, possibly even reflected in the style of the office, e.g. prince-lieutenant in Luxemburg, repeatedly filled by the Crown prince before the grandduke's abdication), or in form of consortium imperii; some have even a practce in which the Monarch can formally abdicate in favor of his Heir, and yet retain a kingly title with executive power, e.g. Maha Upayuvaraja Sanskrit for 'Great Joint King' in Cambodia, though sometimes also conferred on powerful regents who exercised executive powers.
Titular royal princedomsOne type of prince belongs in both the genealogical royalty and the territorial princely styles. A number of nobiliary territories, carrying with them the formal style of prince, are not (or no longer) actual (political, administrative, etc. principalities, but are maintained as essentially hononary titles (though some land, income etc. may be attached to them), and are awarded traditionally (or occasionally) to princes of the blood, as an appanage.
This is done in particular for the heir to the throne (creating a de facto primogeniture), who is often awarded a particular principality in each generation, so that it becomes synonymous with the first in line for the throne, even if there is no automatic legal mechanism to do so.
Examples: UK (originally England) : Prince of Wales Netherlands : Prins van Oranje (Prince of Orange, once a real principality around the homonymous city in southern France) Spain : Principe de Asturias (Prince of the Asturias, once a separate kingdom) Some states have an analogous tradition, where they confer another princely title, such as the British 'royal duchies' (for various royal princes), and formerly the French Dauphin (again, through de facto primogeniture).
Both systems may concur, as in the kingdom Belgium, where "Prince of Liège=Luik" is one of the traditional titles for royal sons (alongside Duke of Brabant, the highest title, being handed down through primogeniture if it is not yet taken; Count of Flanders is similarly used for the next in the succession order).
Titular Princedoms below royaltyIn several countries of the European continent, e.g. in France, prince can be an aristocratic title of someone having a high rank of nobility in chief of a geographical place, but no actual princedom, an d without any necessary link to Royalty, which makes comparing it with e.g. the British system of "royal" princes difficult.
Example: Princess de Polignac (France) This can even occur in a monarchy within which an identical 'real' feudal title exists, such as Fürst in German; e.g. Prince Bismarck in the empire of reunited Germany, under the Hohenzollern dynasty.
In other cases, such titular princedoms (the same happens with other titular awardings at peerage level) is created in chief of an event, such as a treaty (e.g. minister Manuel Goday was created Principe de la Paz 'Prince of Peace' by his Spanish king for negocating the 1795 double peace treaty of Basilea, by which the revolutionary French republic made peace with Prussia and with Spain) or more confusingly in chief of the battleground (or a nearby locality) where a victory was won, even if the awarding monarch has no authority in that country outside his realm (Napoleon Bonaparte created many such titles, e.g. duc de Marengo).
RussiaIn the Russian system, knyaz (translated as "prince"), is the highest degree of nobility, and sometimes, represents a mediatization of an older native dynasty which became subject to the Russian imperial dynasty. Rurikid branches used the knyaz title also after they were succeeded by the Romanovs as the Russian imperial dynasty.