Mumin

Mu'min or mumin is an Arabic name and Islamic term frequently referenced in the Quran, meaning 'believer'. Al-Mu'minun is the 23rd chapter (sūrah) of the Qur'an.

In the Quran

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". Also, it is used as a name and one of the names of God. The opposite term of iman is kufr, and the opposite of mumin is kafir.
The Quran states:
This verse addresses the believers, exhorting them to believe, implying multiple stages of belief.
There is a difference between the terms Muslim and mumin. The term mumin is the preferred term used in the Quran to describe monotheistic believers.