Ātman (Skt.). For Hindus and Sikhs, the real or true Self, which underlies and is present in human appearance. In the Vedas, that sense had not developed. In the Ṛg Veda it means breath, or the whole body, as opposed to parts of it. It may even simply be a reflexive pronoun (cf. nafs in Arabic). It was only in the period of the Āraṇyakas and Upaniṣads that attempts were made to define and describe the nature of this ‘self’ more precisely. Brihādaranyaka Upaniṣad 1. 3. 22 states that the vital force, ātman (now much more than breath) is present and operative in every form of life, not just in humans. Ātman is therefore necessarily identical with Brahman.

In Buddhism, this idea of ātman was profoundly contradicted: see ANĀTMAN (= anatta). For Sikhs, the immortal ātman is the means of relation to God—indeed, the union (for those who attain it) is so close that it comes close at times to identity: ‘God abides in the ātman, and the ātman abides in God’ (Ādi Granth 1153).

Atman

Usually translated "Soul" but better rendered "Self." In the Hindu religion, Atman means the union of the collective human soul with God (Brahma), eventually merged in the absolute totality of Brahman. It is believed that the soul is neither body nor mind, nor even thought, but that these are merely conditions by which the soul is clouded so that it loses its sense of oneness with God. In the Upanishads it is said, "The Self, smaller than small, greater than great, is hidden in the heart of the creature" and "In the beginning there was Self."

Sources:

Davis, Roy Eugene. The Path of Soul Liberation. Lakemont, Ga.: CSA Press, 1975.

Mishra, Shri Ramamurti. Self Analysis and Self Knowledge. Lakemont, Ga.: CSA Press, 1977.

Prabhavananda, Swami, with Frederick Manchester. The Spiritual Heritage of India. Garden City, N.Y.: Doubleday, 1963.

at·man / ˈätmən/ (also At·man) • n. Hinduism the spiritual life principle of the universe, esp. when regarded as inherent in the real self of the individual. ∎  a person's soul.

atman in Hindu philosophy, the spiritual life principle of the universe, especially when regarded as immanent in the real self of the individual. Various strands in Hindu thought differ in the way they regard the relationship (or identity) of the individual atman or ‘self’ and the universal Atman.

The word comes from Sanskrit ātman, literally ‘essence, breath’.

atman Human soul or self in Hindu religion. See Brahman