Sultan is an Islamic title, with several historical meanings. Originally it was an Arabic language abstract noun meaning "strength", "authority", or "rulership", derived from the masdar, meaning "authority" or "power". Later, it came to be used as the title of certain Muslim rulers who claimed almost full sovereignty in practical terms (i.e., the lack of dependence on any higher ruler), without claiming the overall Caliphate, or it was used to refer to a powerful governor of a province within the caliphate. It then developed some further meanings in certain contexts.
The dynasty and lands ruled by a sultan are referred to as a sultanate.