What are kshetra and kshetrajna in the Bhagavad Gita?

Bhagavad Gita chapter 13 opens with Krishna introducing a distinction he calls foundational to spiritual knowledge: "This body, O son of Kunti, is called the field (kshetra), and one who knows it is called the knower of the field (kshetrajna) by those who discern the truth about them" (13.1-2, per the standard verse numbering that includes the opening verse in some editions). The kshetra — the "field" — is the body and the entire arena of material experience: the physical form, the senses, the mind, and the ego through which a person interacts with the world, described as the ground in which the results of past actions are sown and reaped, much like crops in farmland. The kshetrajna — the "knower of the field" — is consciousness itself, the witnessing awareness present within the body but distinct from it, aware of the field's changes without itself changing. Krishna states that he himself, as the Supreme, is also the kshetrajna in every field, every body (13.3) — meaning the individual self's capacity to know and witness is itself an expression of the same universal consciousness rather than something wholly separate from it. The chapter goes on to list the qualities that constitute true knowledge (jnana) — humility, non-violence, patience, purity, self-control, and freedom from attachment to one's body, spouse, home, or possessions (13.8-12) — treating right knowledge as inseparable from a specific way of living rather than as abstract doctrine. The chapter's larger teaching is that liberation depends on learning to distinguish the field (the perishable body and its experiences) from the knower (the unchanging witness), since confusing the two — identifying entirely with the body — is, in the Gita's account, the root of bondage and suffering.