Isotopy
A Homotopy from one embedding of a Manifold 
in 
to another such that at every time, it is anembedding. The notion of isotopy is category independent, so notions of topological, piecewise-linear, smooth, isotopy (and so on) exist. When no explicit mention is made, ``isotopy'' usually means ``smooth isotopy.''
- Fermat's Problem
- Fermat's Right Triangle Theorem
- Fermat's Sigma Problem
- Fermat's Simple Theorem
- Fermat's Spiral
- Fermat's Theorem
- Fermat's Two-Square Theorem
- Fermat Sum Theorem
- Fermi-Dirac Distribution
- Fern
- Ferrari's Identity
- Ferrers Diagram
- Ferrers' Function
- Ferrier's Prime
- Feuerbach Circle
- Feuerbach Point
- Feuerbach's Conic Theorem
- Feuerbach's Theorem
- Feynman Point
- FFT
- Fiber
- Fiber Bundle
- Fiber Space
- Fibonacci Dual Theorem
- Fibonacci Hyperbolic Cosine