In the Upaniṣads as well as in the Bhagavadgītā the three words adhibhūta, adhidaiva and adhyātma are frequently met with. The indeclinable ‘adhi’ has the sense of ‘ruling over,’ ‘pertaining to’. The word ‘ātman’ is often used in the sense of the body. Hence ‘adhyātma’ generally indicates the Self within the body which resides in it and rules over it. It is also used to indicate Brahman or the Supreme Self.
The word is also used as an adjective and in combination with other words. For instance: adhyātmavidyā (knowledge of the Self), adhyātmayoga (yoga or meditation on the Self).