Free public beta until December 4, 2026: every course is open, no card needed. After that, the first chapter of each course stays free and full access is a one-time $39 ($19 for up to 100 founding members chosen for helpful feedback). Your progress is kept. How the beta works

faithful action

A group action in which the only element fixing every point of $X$ is $e$ itself -- the kernel $\bigcap_{x\in X}\operatorname{Stab}(x)$ is trivial.

Examples

$D_4$ acting on a square's vertices is faithful: only the identity symmetry fixes every vertex.