**ABACUS **- Instrument for counting and calculation. Calculator with several metal rods, holding balls that can be manipulated, serving to perform mathematical operations.

**ABSCISSA - **Axis coordinate name **x** in a two-dimensional Cartesian system.

**ADDITION -** One of four basic arithmetic operations, used to add one number to another.

**ALPHA (****) - **First letter of greek alphabet.

**DIGITAL** - Symbols used to represent numbers. In our base numbering system 10, there are ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9.

**LINEAR ALGEBRA** - Branch of Mathematics that uses some fundamental concepts and structures, such as: vectors, vector spaces, linear transformations, systems of linear equations and matrices.

**Algorithm - **A set of rules required to solve a problem or calculation.

**ALIQUOT** - Percentage with which a certain tax is levied on the value of the taxed object.

**HEIGHT** - Dimension of a body considered vertically from bottom to top.

**SAMPLE - **A set chosen to represent a collection or population.

**RANGE OF AN INTERVAL** - It is the difference between the upper and lower end of the range. Also called gap diameter.

**ANGLE - **Angle is the joining of two oriented straight line segments (or two oriented straight lines) from a common point. The intersection between the two segments (or half-straight) is called the vertex of the angle and the sides of the angle are the two segments (or half-straight).

**ADJACENT ANGLE -** Angle with one vertex and one common side. The angles GED and DEF are adjacent.

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**ACUTE ANGLE** - Angle measuring less than 90º and more than 0º.

**ANGLE**** OBTUSE** - Angle measuring more than 90º and less than 180 degrees.

**Shallow Angle - **Angle that measures exactly 180º.

**STRAIGHT ANGLE** - Angle that measures exactly 90º.

**ADDITIONAL ANGLES - **Angles whose sum is equal to 90º.

**ADDITIONAL ANGLES** - Two angles are said to be supplementary when their sum is 180º.

**RING (Geometry) - **Plane portion delimited by two circles with the same center.

**YEAR** - Time period comprising 365 days, except the leap year, which has 366 days.

**APOTHEM** - Perpendicular line segment next to a polygon drawn from its center.

**APPROACH - **Value obtained by rounding a measure. Example: If we rounded the number 6.851 we would have 6.85.

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