Let XX be a . An Ω⊂X\Omega\subset X is said to be parallel to a L⊂XL\subset X if

Ω=ω+L\Omega=\omega+L

for some ω∈Ω\omega\in\Omega.

Examples
  • In Rn\mathbb{R}^n, any affine subspace is parallel to its direction subspace (the translation of the affine set through the origin).
Remarks

By , every nonempty affine set is parallel to at least one subspace. The parallel subspace is unique and can be written explicitly as Ω−Ω\Omega-\Omega; see .