Abscissa
The 
- (horizontal) coordinate of a point in a two dimensional coordinate system. Physicists and astronomers sometimesuse the term to refer to the axis itself instead of the distance along it.
- Conway Polynomial
- Conway Puzzle
- Conway's Constant
- Conway Sequence
- Conway's Game of Life
- Conway's Knot
- Conway's Knot Notation
- Conway's Life
- Conway Sphere
- Coordinate Geometry
- Coordinates
- Coordinate System
- Coordination Number
- Copeland-Erdös Constant
- Coplanar
- Coprime
- Copson-de Bruijn Constant
- Copson's Inequality
- Copula
- Cork Plug
- Corkscrew Surface
- Cornish-Fisher Asymptotic Expansion
- Cornucopia
- Cornu Spiral
- Corollary