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.- C*
- Cable Knot
- Cactus Fractal
- Cake Cutting
- Cal
- Calabi's Triangle
- Calabi-Yau Space
- Calculus
- Calculus of Variations
- Calcus
- Calderón's Formula
- C*-Algebra
- Caliban Puzzle
- Calvary Cross
- Cameron's Sum-Free Set Constant
- Cancellation
- Cancellation Law
- Cannonball Problem
- Canonical Form
- Canonical Polyhedron
- Canonical Transformation
- Cantor Comb
- Cantor-Dedekind Axiom
- Cantor Diagonal Method
- Cantor Diagonal Slash