Thank you for your question. In some translations of the Qurʾān the term nafs is translated in almost every instance it appears as the soul. This can be misunderstood as although the term is used to denote the spiritual aspect of the human in some instances, in many others it is better translated as the individual, rather than specifically the soul or spiritual aspect of the human. It is not a completely incorrect use of the word soul as it can be used to mean an individual in English too, like in the phrase: “don’t tell a soul”. It is more that we are aware of the context of such a phrase and therefore would not misinterpret it to mean “don’t tell a spiritual aspect of an individual”.

The spiritual element of a human is also referred to in other instances as the rūḥ, especially in the story of the creation of Adam (see 32:9; 15:29; 38:72), although the term rūḥ doesn’t always denote spiritual aspect of the human either (see for example 40:15; 16:2; 97:4). 

The rūḥ and nafs are not interchangeable terms. 

It is a later philosophical development which equates the nafs with the soul of the human and that has perhaps caused some confusion regarding the linguistic meaning of nafs used in the Qurʾān.

The term nafs and its derivatives occur more than 250 times in the Qurʾān and it denotes the individualisation of an essence. A referent of this general term is the human nafs (other referents include jinn 6:130 including Satan 18:51 and God Himself see 6:12), either:

1. in terms of its inner or spiritual aspect, with the commanding soul, al-nafs al-ammārah (see 12:18; 12:53; 20:96, 50:16; 64:16; 53:23; 59:9) where Satan whispers (see 47:25) and if fought results in heaven (see 70:40-41). The commanding self is fought with the blaming self or conscience, al-nafs al-lawwāmah (75:2) so that a person reaches a clear conscience al-nafs al-muṭmainnah (89:27)

2. or in terms of an individual, as when Moses said: “Lord, I have killed a person (nafs) among them, and I fear they will kill me!” (see 28:33; also for example 2:155; 5:45; 17:33; 18:74; 25:68; 61:11)

References

* Al-Muṣṭafawī, Taḥqīq fī kalimāt al-Qurʾān al-Karīm, (12) 196-199.

* Emil Homerin, “Soul” in Encyclopaedia of the Qurʾān, Brill, (5) 80-84