Klein geometry

Short definition from Wiktionary

Noun

1. 1
   A type of geometry (mathematical object representing a space and its spatial relationships); a homogeneous space X together with a symmetry group which represents the group action on X of some Lie group;
2. 2
   A type of geometry (mathematical object representing a space and its spatial relationships); a homogeneous space X together with a symmetry group which represents the group action on X of some Lie group; (more formally) an ordered pair (G, H), where G is a Lie group and H a closed Lie subgroup of G such that the left coset space G / H is connected: an ordered pair (G, H), where G is a Lie group an
3. 3
   The coset space G / H.