Rodrigues's Curvature Formula
where
is the unit Normal Vector and 
is one of the two Principal Curvatures.See also Normal Vector, Principal Curvatures- Extrinsic Curvature
- Fabry Imbedding
- Face
- Facet
- Faceting
- Factor
- Factor Base
- Factor (Graph)
- Factor Group
- Factorial
- Factorial Moment
- Factorial Number
- Factorial Prime
- Factorial Sum
- Factoring
- Factorion
- Factorization
- Factor Level
- Factor Ring
- Factor Space
- Fagnano's Point
- Fagnano's Problem
- Fagnano's Theorem
- Fair Game
- Fairy Chess