Proper Divisor
A Divisor of a number 
excluding itself.
- Pedal Point
- Pedal Triangle
- Peg Knot
- Peg Solitaire
- Peg Top
- Peirce's Theorem
- p-Element
- Pell Equation
- Pell-Lucas Number
- Pell-Lucas Polynomial
- Pell Number
- Pell Polynomial
- Pell Sequence
- Pencil
- Penrose Stairway
- Penrose Tiles
- Penrose Triangle
- Penrose Tribar
- Pentabolo
- Pentacle
- Pentacontagon
- Pentad
- Pentadecagon
- Pentaflake
- Pentagon