Definition
Plain language
A tidy formula you can write out and evaluate directly, instead of grinding through repeated calculation.
As stated in the literature
A closed-form expression solves a problem with a finite combination of standard operations and functions rather than an iterative or numerical procedure; e.g., a diffusion term that becomes exact algebra in a Fourier basis, avoiding step-by-step approximation.
Also called: closed form
Why it matters: It matters because a direct formula is usually faster and exact, avoiding the slow, error-prone grind of repeated approximation.
For example, instead of adding up a series step by step, you might have a single formula that gives the exact answer in one shot.
Heard on the show
“Then it derives the posterior in closed form, and every matched round roughly doubles the odds that you're facing yourself.”Episode 234 — Two Copies of Gemini Cooperated in a Game Where Betrayal Always Pays