Inclusion-Exclusion Principle
If 
, ..., 
are finite sets, then
where
is the sum of the Cardinalities of the intersections of the sets taken 
at a time.- Coupon Collector's Problem
- Covariance
- Covariance Matrix
- Covariant Derivative
- Covariant Tensor
- Covariant Vector
- Cover
- Covering
- Covering Dimension
- Covering System
- Cover Relation
- Coversine
- Coxeter Diagram
- Coxeter-Dynkin Diagram
- Coxeter Graph
- Coxeter Group
- Coxeter Matrix
- Coxeter's Loxodromic Sequence of Tangent Circles
- Coxeter-Todd Lattice
- Cox's Theorem
- Cramer's Rule
- Cramér Conjecture
- Cramér-Euler Paradox
- Cramér's Theorem
- Craps