surface normal

Short definition from Wiktionary

Noun

1. 1
   A unit vector at any given point P of a surface M which is perpendicular to the tangent plane T_P(M) of M at P. For a surface with parametrization ⃑x(u,v), it is given by
2. 2
   A unit vector at any given point P of a surface M which is perpendicular to the tangent plane T_P(M) of M at P. For a surface with parametrization ⃑x(u,v), it is given by ⃑n=±⃑x_u×⃑x_v/ lVert ⃑x_u×⃑x_v rVert where the sign can be chosen at will: ⃑n=±⃑x_u×⃑x_v/ lVert ⃑x_u×⃑x_v rVert
3. 3
   A unit vector at any given point P of a surface M which is perpendicular to the tangent plane T_P(M) of M at P. For a surface with parametrization ⃑x(u,v), it is given by ⃑n=±⃑x_u×⃑x_v/ lVert ⃑x_u×⃑x_v rVert where the sign can be chosen at will: where the sign can be chosen at will.