tamas
Darkness; sorrow; dullness; the ignorance guṇa.
In Vedanta
The guṇa of inertia, dullness, and concealment. A tāmasika mind is characterized by lethargy, confusion, negligence, and resistance to inquiry. Tamas conceals the nature of things, contributing to fundamental ignorance. In the creation model, tamas in each element produces the gross physical world. Tamas is overcome by rajas (activity), and rajas is refined into sattva through disciplined living.