Abacus - A primitive calculator, designed before the discovery of electricity. Although limited, there is a certain pleasure in gently sliding the beads from one side to the other, as a visual representation of mathematical functions.
Absolute Value / abs(x) / |x| - A declaration to allow even the most negative of heart to become positive.
Acute - (1) An angle below 90 degrees (or π/2 radians)
(2) Something so irresistibly adorable, it requires an extra 'A' before proclaiming it as cute.
Addition - (1) Taking two or more numbers and combining their value, usually to increase it.
(2) "In addition", a wonderful way to extend the length of any lecture to keep young people gripped and on the edge of their seats.
(3) The sum of definitions (1) and (2)
Algebra - (1) A method of numerical notation, the primary purpose of which is to ensure that the maths community remains relatively small by scaring away the majority of budding mathematicians.
(2) A fine example of how the Latin and Greek alphabets can work in harmony with numbers to cause beautiful confusion and enlightenment in equal measure.
Algorithm - A precise set of steps leading invariably to a single answer, usually used in computer programming, but if one wishes to partake in algorithmic calculation, one would find it most rewarding.
Angle - (1) The amount of turning around a point one line must do to meet another.
(2) "A different angle", another way to admire the beauty of maths in addition to a previous glorious viewpoint.
Arc - (1) A curved line forming part of a circle, segment or sector.
(2) The way that any object falls after being given velocity, almost as if all things love to obey maths. I would not be surprised if gravity was proven to be the attractive force of maths itself.