abacus a device for calculating; can use beads or counters. more info
acute describes an angle between 0° and 90°.
addend any number which is to be added: 2 + 5 = 7 (2 and 5 are addends).
adjacent adjoining (as used to describe lines and angles).
adjacent angles Angles which have the same vertex and a line in common are called adjacent angles.
algorithm A procedure or formula for solving a problem. The word
derives from the name of the mathematician, Mohammed ibn-Musa Al-Khowarizmi, who was part of the royal court in Baghdad and who lived from about 780 to 850.
alternate every other one in a sequence.
altitude of a triangle The line drawn from a vertex of a triangle to meet the opposite site at right angles. more info
analog clock A clock face with numbers 1 to 12 and two hands
angle the number of degrees rotated around a point.
apex The highest point where two or more lines meet to form a corner of a figure or solid.
aproximation A result that is almost accurate. Rounding to the next highest whole number is an approximation
arbitrary units non-standard units such as hand spans, counters and hand claps.
arc part of the circumference of a circle.
area the amount of space within a perimeter (expressed in square units).
array the arrangement of the units of a number in rows and columns (e.g., 6 = :::).
ascending order the arrangement of numbers from smallest to largest.
associative An operation is associative if when three elements are combined it does not matter how the brackets are placed. Ex:
(x*y)*z=x*(y*z). more info
average a number representing a set of numbers (obtained by dividing the total of the numbers by the number of numbers in the set). See "mean".
axis (of symmetry) a line dividing a shape into two symmetrical parts.