Right Angle
An Angle equal to half the Angle from one end of a line segment to the other. A right angle is 
radians or 90°. A Triangle containing a right angle is called a Right Triangle. However, aTriangle cannot contain more than one right angle, since the sum of the two right angles plus the third angle wouldexceed the 180° total possessed by a Triangle.
- Stieltjes-Wigert Polynomial
- Stirling Cycle Number
- Stirling Number of the First Kind
- Stirling Number of the Second Kind
- Stirling's Approximation
- Stirling Set Number
- Stirling's Finite Difference Formula
- Stirling's Formula
- Stirling's Series
- Stirrup Curve
- Stochastic
- Stochastic Calculus of Variations
- Stochastic Group
- Stochastic Matrix
- Stochastic Process
- Stochastic Resonance
- Stokes Phenomenon
- Stokes' Theorem
- Stolarsky Array
- Stolarsky-Harborth Constant
- Stolarsky's Inequality
- Stomachion
- Stone Space
- Stone-von Neumann Theorem
- Stopper Knot