Why: Krishna answers that the wise understand renunciation as giving up desire-driven action, while the learned call relinquishing the fruits of all action, relinquishment, giving crisp, distinct definitions for two terms that had been used somewhat interchangeably.

In life: two related concepts you've been treating as roughly interchangeable, boundaries and distance, discipline and restriction, might actually deserve sharper, distinct definitions once you look closely.

Teaching: pick two concepts in your own thinking that you've been treating as roughly interchangeable, and try defining each one precisely and distinctly, the exercise itself often reveals a useful difference you'd been missing.