Collinear
Three or more points 
, 
, 
, ..., are said to be collinear if they lie on a single straight Line 
.(Two points are always collinear.) This will be true Iff the ratios of distances satisfy
Two points are trivially collinear since two points determine a Line.See also Concyclic, Directed Angle, N-Cluster, Sylvester's Line Problem
- Cascade
- Casey's Theorem
- Casimir Operator
- Cassini Ellipses
- Cassini Ovals
- Cassini Projection
- Cassini's Identity
- Cassini Surface
- Castillon's Problem
- Casting Out Nines
- Catacaustic
- Catalan Integrals
- Catalan Number
- Catalan's Conjecture
- Catalan's Constant
- Catalan's Diophantine Problem
- Catalan Solid
- Catalan's Problem
- Catalan's Surface
- Catalan's Triangle
- Catalan's Trisectrix
- Catastrophe
- Catastrophe Theory
- Categorical Game
- Categorical Variable