V. S. Apte, The Practical Sanskrit–English Dictionary. Look up any word of the Gita in Devanagari, IAST or Harvard-Kyoto, or browse the headwords letter by letter.
adhibhūtaṁ kṣaro bhāvaḥ puruṣaścādhidaivatam, — adhibhūtam is kṣaraḥ bhāvaḥ, adhidaiva is the Purusha; I myself am the Lord of sacrifice, adhiyajña here in the body, O best of embodied beings. 8·4
क्षरःkṣaraḥnominative singular of the masculine form of the adjective kṣara (mutable becoming) used as a noun.
क्षरम्kṣaramaccusative singular of the masculine form of the adjective kṣara (the mutable)used as a noun.