[1][2] Not all living organisms are referred to as Nefesh, arthropods ("bugs") and plants, for example, are not described in the Bible as nephesh.
The primary meaning of the term נפש is 'the breath of life' instinct in the nostrils of all living beings, and by extension 'life', 'person' or 'very self'.
There is no term in English corresponding to nephesh, and the (Christian) 'soul', which has quite different connotations is nonetheless customarily used to translate it.
Nephesh when put with another word can detail aspects related to the concept of nephesh; with רוּחַ rûach (“breath”, “wind,” or "spirit") it describes a part of mankind that is immaterial, like one's mind, emotions, will, intellect, personality, and conscience, as in Job 7:11.
In Greek, the word ψυχή (psyche) is the closest equivalent to the Hebrew nephesh.