Absolute zero - The lowest possible temperature. A state of no energy of motion or vibration, especially at the molecular scale. Zero degrees Kelvin. See Celsius, Fahrenheit. See also the explanation on temperature conversions.

Absolute value - The unsigned value (magnitude) of a number. In practice, drop the negative sign, if any. An equation with a constant absolute term

Acute - An angle less than 90 degrees. See obtuse, right angle.

Addition - A shortcut for counting up from zero by all the numbers to be added. The arithmetic can be checked by subtraction or by adding in reverse order (addition is commutative).

Adjacent - Next to. See adjacent angles, adjacent leg, adjacent side of a triangle, adjacent side of a polygon.

Adjacent angles - Angles forming a common line segment. The vertex of each angle forms one endpoint of the segment. The angles are therefore adjacent or next to the segment.

Adjacent leg - The side of a right triangle next to the measured angle. The side of a right triangle which has the vertex of the reference angle (measured angle) as an endpoint. See trigonometry.

Adjacent side of a triangle - The side of a triangle next to the measured angle. The side of a triangle which has the vertex of the reference angle (measured angle) as an endpoint.

Adjacent side of a polygon - The side of a polygon next to the measured side. The side of a polygon which has an endpoint of the measured side as an endpoint.

Altitude - The greatest distance from the base of a figure to any other point on the figure. By definition the distance is measured along a line perpendicular to the base. The height of a figure.

Amount - The quantity of a given class of item or the measure of a given unit. Sometimes used to refer to the balance of a savings account after the compounding of interest. See number, value.

Angle - The union of two rays with a common endpoint called the vertex of the angle. See angle measure.

Angle measure - The amount of rotation of a ray around its endpoint. The rotation is measured relative to another ray with the same endpoint. The two rays form the side of the angle. The rotation is measured in degrees (360ths of a circle) or in radians (2 pi radians to a circle). Equals the arc measure of the part of a circle or arc intercepted by the rays of an angle having its vertex at the center of the circle. See central angle. Note: In geometry it is often necessary to distinguish between the angle measure and the angle itself.

Annual - Once per year. Yearly. Used as the basis for stating rates of interest on savings accounts or loans.

Anti-logarithm - The inverse of a logarithmic value of a base raised to a power.

Apex - The point on a pyramid or cone farthest from the base. The pointed end of the pyramid or cone. See altitude.

Approximate - Close in value to the actual number. Resulting from an estimate. See rounding.

Arc - Part of a circle. The arc may be measured in degrees or in radians or by its arc length. See angle measure.

Arc length - The distance along the curve of an arc. The arc length of a circle is equal to its circumference. See arc measure.

Arc measure - The measure of an arc in 360ths of a circle (degrees) or in radians. Equals the measure of an angle having its vertex at the center of the circle. See central angle, arc length.

Arc segment - A contiguous portion of an arc, finite in length and terminated by two endpoints, one at each end. The distance along the path of the arc between the endpoints is equal to the arc length of the segment.

Arc-function - The angle which has the given value for the given trigonometric function.

Area - The amount of surface of a figure or cross-section, usually measured in square units. A two-dimensional measure of size. See volume, length.

Arithmetic - The study or technique of processing numbers by means of calculations, usually to reach an answer to a problem. See mathematics.

Associative - More than two successive additions can be done in any order without changing the result of the calculation. More than two successive multiplications can be done in any order without changing the result of the calculation. See commutative property.

Average - Mean. The sum of a set of values divided by the number of values.

Axis - A line of radial symmetry or rotation. See axis of rotation.

Axis of rotation - A line in space around which a figure turns. The figure does not necessarily exhibit radial symmetry See axis of rotation.

Axis - A line around which a figure in three dimensions exhibits radial symmetry. See axis of rotation.

Lasted updated 6/2/97 - 4/10/2000.