WALĀYAH, or wilāyah, an Arabic verbal noun derived from the root wly, carries the basic meanings of "friendship, assistance" and "authority, power." A fundamental notion of Islamic social and spiritual life, the term is used with a complex variety of meanings related to the function, position, authority, or domain of authority of a walī (pl., awliyāʾ; "next of kin, ally, friend, helper, guardian, patron, saint"); a mawlā (pl., mawālī; "cousin, close relation, ally, client, patron, master"); or a wālī (pl., wulāh; "administrator, governor, ruler"). It appears in Persian as valāyat, vilāyat, and in Turkish as vilayet.

A distinction is often made between walāyah and wilāyah, with the latter form generally preferred to convey the meaning of "power," "authority," or "domain of authority" (e.g., a political subdivision of a country). However, the vocalization is not...