Kṣetra-Kṣetrajña Yoga · Verse 2
श्रीभगवानुवाच | इदं शरीरं कौन्तेय क्षेत्रमित्यभिधीयते | एतद्यो वेत्ति तं प्राहुः क्षेत्रज्ञ इति तद्विदः
śrī-bhagavān uvāca | idaṃ śarīraṃ kaunteya kṣetram ity abhidhīyate | etad yo vetti taṃ prāhuḥ kṣetra-jña iti tad-vidaḥ
The Blessed Lord said: This body, O son of Kuntī!, is called the field, and one who knows it, those who know the Truth call him the knower of the field.
Kṛṣṇa defines the key terms: the kṣetra is the physical-psychic body, not just anatomy, but the entire complex of guṇas that constitute the empirical personality.
The kṣetra-jña — knower of the field — is pure consciousness that observes, distinct from the observed field. This distinction (bheda) is the foundation of discrimination (viveka).
The expression tad-vidaḥ — “those who know that” — are the teachers (ācāryas) whose authority legitimates the definition. This is not individual speculation, but transmitted wisdom.