Areal Coordinates
Trilinear Coordinates normalized so that
When so normalized, they become the Areas of the Triangles
, 
, and
, where 
is the point whose coordinates have been specified.- Aschbacher's Component Theorem
- A-Sequence
- Associative
- Associative Algebra
- Associative Magic Square
- ASS Theorem
- Astroid
- Astroidal Ellipsoid
- Astroid Evolute
- Astroid Involute
- Astroid Pedal Curve
- Astroid Radial Curve
- Asymptosy
- Asymptote
- Asymptotic
- Asymptotic Curve
- Asymptotic Direction
- Asymptotic Notation
- Asymptotic Series
- Atiyah-Singer Index Theorem
- Atkin-Goldwasser-Kilian-Morain Certificate
- Atomic Statement
- Attraction Basin
- Attractor
- Auction