Nafs. The soul. The Arabic nafs corresponds to the Latin anima and the Greek psyche. It is the individual substance, and corresponds to the receptive pole of Being. It exists alongside ruh (“spirit”), corresponding to Latin spiritus and Greek pneuma, which is non-individual and represents the active pole of Being in man, also called the ‘aql (“Intellect”).
Often the term nafs is used in a pejorative sense, because in its fallen, unregenerate state, admixed with passion and ignorance, it is an-nafs al-ammarah bi-s-su (“the soul which incites to evil”, 12:53). Passing through the stage of an-nafs al-lawwamah (“the reproachful soul”, 75:2), which corresponds in a way to conscience advocating conversion, it can become purified and reconciled to the source of its reality as an-nafs al-mutma’innah (“soul at peace”) assured of paradise:
‘O soul at peace, return unto thy Lord, well-pleased, well-pleasing! Enter thou among my servants! Enter thou My paradise!’ (89:27)
Source: Cyril Glassé, The Concise Encyclopedia of Islam, Third Edition, p. 388