Kāfir (Arabic: كافر; pl. كافرون, kāfirūn) is an Islamic term of Arabic origin used by Muslims to refer to non-Muslims who deny Allah, reject his authority, and do not accept the message of Islam as truth.
Kafir is often translated as 'infidel', 'truth denier', 'rejector', 'disbeliever', 'unbeliever', The term is used in different ways in the Quran, with the most fundamental sense being ungrateful towards God. Kufr means 'disbelief', 'unbelief', 'non-belief', 'to be thankless', 'to be faithless', or 'ingratitude'. The opposite term of kufr ('disbelief') is iman ('faith'), and the opposite of kafir ('disbeliever') is mu'min ('believer'). A person who denies the existence of a creator might be called a dahri.