affine algebraic group
An affine algebraic group over a field is quasi-affine variety (a locally closed subset of affine space) over , which is a equipped with a group such that the multiplication map and inverse map are algebraic.
For example, is an affine algebraic group over itself with the group law being addition, and as is with the group law multiplication. Other common examples of affine algebraic groups are , the general linear group over (identifying matrices with affine space) and any algebraic torus over .