Tawḥīd (also Tawheed, and other spellings) (Arabic: توحيد) is the Islamic concept of monotheism, derived from the root word Ahad. In Arabic, Tawhīd means 'unification', i.e. to unify or to keep something unified. In Islam, Tawhīd means to assert the unity of God. The opposite of Tawhīd is shirk, which means "division" in Arabic. Muslims view polytheism and idolatry as shirk.