Mumin denotes a person who has complete submission to the will of God and has faith firmly established in his heart, i.e. a "faithful Muslim".[1] Also, it is used as a name and one of the names of God.[1] The opposite term of iman (faith) is kufr (disbelief), and the opposite of mumin is kafir (disbeliever).[2][3][4]
O believers! Have faith in Allah, His Messenger, the Book He has revealed to His Messenger, and the Scriptures He revealed before. Indeed, whoever denies Allah, His angels, His Books, His messengers, and the Last Day has clearly gone far astray.
^Willis, John Ralph, ed. (2018) [1979]. "Glossary". Studies in West African Islamic History, Volume 1: The Cultivators of Islam (1st ed.). London and New York: Routledge. p. 197. ISBN9781138238534. Kufr: Unbelief; non-Muslim belief (Kāfir = a non-Muslim, one who has received no Dispensation or Book; Kuffār plural of Kāfir).