1.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.

1.这些观察允许我们形式化反射: 反射是欧里得空间等距同构，它不动点集是余维度为 1 仿射子空间。