kośaḥ
Sheath (five of which as though cover ātmā); treasury; dictionary.
In Vedanta
The five sheaths (pañcakośa) that seemingly cover ātmā: annamaya (food/physical), prāṇamaya (vital breath), manomaya (mind), vijñānamaya (intellect), and ānandamaya (bliss). The Taittirīya Upaniṣad uses the kośa model to guide the student inward — each sheath is progressively subtler, and ātmā is recognized as distinct from and pervading all five. The sheaths are not layers to be removed but misconceptions to be resolved.