Karma

No Sanskrit word has travelled further into English with less of its meaning intact. Before anything else: karman simply means act, action, performance, business, attested from the Ṛgveda onward. It is the ordinary word for work. A priest's karma is the ritual he performs; a farmer's karma is farming.

Everything that has grown around it is a set of claims about what actions do — and those claims were argued over, not assumed.

The Bṛhadāraṇyaka gives the classical formulation, and it is worth having in full because the popular version is a truncation.

This person is made of desire. As is his desire, so is his resolve; as is his resolve, so is the action he does; as is the action he does, so does he attain.