Euclidean Plane
The 2-D Euclidean Space denoted 
.
- Splitting Algorithm
- Sponge
- Sporadic Group
- Sports
- Sprague-Grundy Function
- Sprague-Grundy Number
- Sprague-Grundy Value
- Spread (Link)
- Spread (Tree)
- Spun Knot
- Squarable
- Square
- Square Bracket Polynomial
- Square Cupola
- Square Curve
- Square Cutting
- Squared
- Squared Square
- Square-Free
- Squarefree
- Butterfly Catastrophe
- Butterfly Curve
- Butterfly Effect
- Butterfly Fractal
- Butterfly Polyiamond