What is "indicatrix"

Indicatrix \In`di*ca"trix\, n. [NL.] (Geom. of Three Dimensions) A certain conic section supposed to be drawn in the tangent plane to any surface, and used to determine the accidents of curvature of the surface at the point of contact. The curve is similar to the intersection of the surface with a parallel to the tangent plane and indefinitely near it. It is an ellipse when the curvature is synclastic, and an hyperbola when the curvature is anticlastic.

n. (context mathematics crystallography English) An ellipsoid whose three axis represent the refractive index of an anisotropic crystal for light following different directions with respect to the crystal axes

Indicatrix may refer to:

• Dupin indicatrix, a conic section which describes the local shape of a surface
• Tissot's indicatrix, which describes and visualizes the distortion of a map
• Indicatrix, a special case of the index ellipsoid used in optics to describe properties of crystals
• Tangent indicatrix, an object in differential geometry related to a closed space curve