BG Chap 8 - Adhibhūta, Adhidaiva and Adhiyajña
Adhibhūta refers to the temporary material body which constantly changes. Viśvanātha says that adhibhūta refers to temporary material objects such as pots and cloth. The physical nature is constantly changing. Material bodies generally pass through six stages: they are born, they grow, they remain for some duration, they produce some by-products, they dwindle, and then they vanish. This physical nature is called adhibhūta.
Adhidaiva refers to the universal form of the Lord, who rules over the devatās such as Āditya and within whom they exist. Since the demigods are included in the gigantic form of the Lord, worship of the Lord in His gigantic material conception or in His transcendental form as Lord Śrī Kṛṣṇa, appeases the demigods and all the other living beings.
Adhiyajña refers to Kṛṣṇa Himself in His form of Paramātmā situated in the body of all living beings, with a form measuring one pradeśa. He inspires worship from within and gives results for that worship. Kṛṣṇa says He alone (eva) is situated as the Paramātmā, although the Paramātmā is only His expansion. This is because the Paramātmā is not different from Him, whereas the other items such as the adhyātma are different from Him.