Ruh. (lit. “spirit”) The word is used in all the possible meanings of “spirit”, but in particular means the non-individual aspect of the soul, the intellect or nous, in Arabic al-‘aql al-fa’al (or fa’il) (“active intellect”), as opposed to the lower individual soul, the psyche, in Arabic an-nafs.
The spirit (ar-ruh) in the individual is continuous with Being itself, al-wujud, or al-‘aql al-awwal (“first intellect”), and is the dignity which exalts man above animals, and even above Angels. This is signified by the ability of Adam in the garden to name the objects of existence, which the Angels could not do and by which they recognized Adam’s superiority over them, except of course Iblis, the devil, who saw in Adam only clay—and not spirit—and so revolted against God.
Within the individual, ar-ruh is also referred to as al-haqiqah (“reality”) or as-sirr (“the secret”).
Source: Cyril Glassé, The Concise Encyclopedia of Islam, Third Edition, p. 445