homothety

noun2

1. •
   An isotropic scaling transformation of an affine space with a single fixed point.

   • The product of two homotheties with the same centre is a homothety with that centre. — 1927
2. •
   A homomorphism from a module M over a ring A to itself of the form ν:x↦ax for some fixed a∈A (especially when M=A; a is said to be the ratio of the homothety, by analogy with the geometric case).