Diameter
The diameter of a Circle is the Distance from a point on the Circle to a point 
Radians away. If 
is the Radius, 
.
- Parabolic Cylindrical Coordinates
- Parabolic Fixed Point
- Parabolic Geometry
- Parabolic Horn Cyclide
- Parabolic Partial Differential Equation
- Parabolic Point
- Parabolic Ring Cyclide
- Parabolic Rotation
- Parabolic Segment
- Parabolic Spindle Cyclide
- Parabolic Spiral
- Parabolic Umbilic Catastrophe
- Paraboloid
- Paraboloidal Coordinates
- Paraboloid Geodesic
- Paracompact Space
- Paracycle
- Paradox
- Paradromic Rings
- Paragyrate Diminished Rhombicosidodecahedron
- Parallel
- Parallel Axiom
- Parallel Class
- Parallel Curve
- Parallelepiped