AATMA: Aatma (self) is the element (part, fraction) of Paramaatma (Supreme Soul) in human being. Hence Aatma and Parmaatma are the same substance. In other words, both are substantially same but qualitatively different. After one’s death, Aatma rejoins the Paramaatma. According to the Sikh philosophy, God resides in Aatma. Through Aatma, man communicates with God. In other words, it is transcendental self. The Sikh connotation of Aatma is different from “soul” (term used in general sense), which means spirit e.g. as ‘soul’ in the proverb: “a man with dead soul.” The meaning of Aatma is different in different schools of the Hindu philosophy. It is a substance (Nyaya- Visheshaka)\ an object of inference (Samkhya); an object of intuition or the Impersonate Absolute of Braham (Upanishadas) or pure consciousness (Vedanta) etc. In the Sikh Scriptures, there are references, which seem to resemble some of the meanings of this term in different schools of the Hindu philosophy but all these references are contextual or relative and not conceptual (hence coincidental).
1.Dictionary Of Sikh Philosophy : Dr. H.S.Dilgeer