Abscissa
Absolute Value
Acute Angle
Acute Triangle
Addend
Additive Inverse
Adjacent Angles
Adjacent Sides
Algorithm
Alternate Angles (Transversal)
Altitude(s) of a Triangle
Angle
Angle Bisector(s) of a Triangle
Angle of Depression
Angle of Elevation
Angles on the Same Side of the Transversal
Apex
Apothem
Approximation
Arc
Area
Arithmetic Mean
Array
Ascending Order
Associative Property
Average
Axes
Axis
Axis of Symmetry