Wahhabism (Arabic: الوهابية‎‎, al-Wahhābiya(h)) or Wahhabi mission (/wəˈhɑːbi, wɑː-/; Arabic: الدعوة الوهابية‎‎, ad-Da'wa al-Wahhābiya(h) ) is a religious movement or branch of Sunni Islam. It has been variously described as "ultraconservative", "austere", "fundamentalist", "puritanical" or "puritan" and as an Islamic "reform movement" to restore "pure monotheistic worship" (tawhid) by scholars and advocates, and as an "extremist pseudo-Sunni movement" by opponents. Adherents often object to the term Wahhabi or Wahhabism as derogatory, and prefer to be called Salafi or muwahhid. The movement emphasises the principle of tawhid (the "uniqueness" and "unity" of God). Its principal influences include Ahmad ibn Hanbal (780–855) and Ibn Taymiyyah (1263–1328).