subspace

These observations allow one to formalize the definition of reflection: a reflection is an involutive isometry of an Euclidean space whose set of fixed points is an affine subspace of codimension 1.

这些观察们形式化反射定义: 反射是欧几里得空间对合等距同构，它动点集合是余维度为 1 仿射子空间。