Unit Square
A Square with side lengths 1. The unit square usually means the one with coordinates (0, 0), (1, 0), (1, 1), (0,1) in the real plane, or 0, 1, 
, and 
in the Complex Plane.
- Archimedes' Lemma
- Archimedes' Midpoint Theorem
- Archimedes' Postulate
- Archimedes' Problem
- Archimedes' Recurrence Formula
- Archimedes' Spiral
- Archimedes' Spiral Inverse
- Arc Length
- Arc Minute
- Arcsecant
- Arc Second
- Arcsine
- Arctangent
- Area
- Area Element
- Areal Coordinates
- Area-Preserving Map
- Area Principle
- Arf Invariant
- Argand Diagram
- Argand Plane
- Argoh's Conjecture
- Argument Addition Relation
- Argument (Complex Number)
- Argument (Elliptic Integral)