Linked from
The 27 pages that link to Isometry, each with the reason it gives.
Metric spaceRelated: It identifies structure-preserving transformations of metric spaces.
Point groupRelated: The geometric symmetries in ordinary point groups preserve distances.
Euclidean planeRelated: Isometries capture the plane’s rigid motions without changing its geometry.
Rigid motionRelated: Rigid motion is the Euclidean-space case of this broader concept.