The difference between the rûh and the nafs – both which can be translated as “soul” or “spirit” – is a question whose full answer depends upon having knowledge of the soul, which is something that is beyond the power of human knowledge.
Allah says: “They ask you concerning the soul (rûh). Say: ‘The soul is of the command of my Lord. Of knowledge, it is only a little that is communicated to you’.” [Sûrah al-Isrâ’: 85]
We can see that the word nafs is used in the Qur’ân in various ways. It is used to refer to the human being as a body and a soul. This meaning is the one most frequently encountered in the Qur’ân.
Allah says: “So turn (in repentance) to your Maker and slay yourselves (the wrong-doers)” [Sûrah al-Baqarah: 54]
Sometimes it refers to the soul and not the body.
Allah says: “Yield up your souls” [Sûrah al-An`âm: 93]
He says: “O contented soul (nafs)! Come back to your Lord, well pleased, and well-pleasing unto Him.” [Sûrah al-Fajr: 27-28].
As for the word rûh, it comes with the meaning of the divine infusion by which life takes place.
Allah says: “When I have fashioned him (in due proportion) and breathed into him of My spirit, fall down in obeisance unto him.” [Sûrah al-Hijr: 29]
By these texts, we can ascertain that the word nafs is more general in meaning than the word rûh, since the word nafs can be used to refer the human entity as a body and a soul or to the soul alone, while the word rûh is restricted in meaning to the divine infusion of life.
And Allah knows best.