abscissa

The first element in a coordinate pair. When graphed in the coordinate plane, it is the distance from the y-axis. Frequently called the x coordinate.

absolute value

The distance of a number from zero; the positive value of a number.

acid

Traditionally considered any chemical compound that, when dissolved in water, gives a solution with a hydrogen ion activity greater than in pure water $(i.e.$ a pH less than $ \color{#16387C}{7.0} $$).$

acute angle

A positive angle measuring less than $ \color{#16387C}{90} $ degrees.

acute triangle

A triangle with all angles measuring less than $ \color{#16387C}{90} $ degrees.

addend

A number which is involved in addition. Numbers being added are considered to be the addends.

addition

Calculating a sum by adding two or more numbers.

additive inverse

The additive inverse of any number $ \color{#16387C}{x} $ is the number that gives zero when added to $ \color{#16387C}{x} .$ Example: the additive inverse of $ \color{#16387C}{5} $ is $ \color{#16387C}{-5} .$

adjacent angles

Two angles that share both a side and a vertex.

algebra

A branch of mathematics in which variables are substituted for unknown values to solve a particular problem.

algorithm

A step-by-step procedure for carrying out computation.

alternate angles

Two angles that are in opposite locations when lines are cut by a transversal.

altitude

Length from the uppermost point of a triangle to the line opposite.

angle

The union of two rays with a common endpoint, called the vertex.

anion

An ion with more electrons than protons, giving it a net negative charge.

annulus

The portion of a plane bounded by two concentric circles in the plane.

antiderivative

An antiderivative of a function $ \color{#16387C}{f} $ is a function $ \color{#16387C}{F} $ whose derivative is equal to $ \color{#16387C}{f} $$.$ Example: $ \color{#16387C}{F'=f} $$.$

approximate

Estimate.

arc

A portion of the circumference of a circle.

area

The number of square units covering a shape or figure.

arithmetic

Method of computing using addition, subtraction, multiplication, or division.

arithmetic sequence

A sequence with the difference between two consecutive terms constant. The difference is called the common difference.

array

A set of numbers that will follow a specific pattern. An orderly arrangement often in rows, columns or a matrix.

associative property

When performing an operation on three or more numbers, the result is unchanged by the way the numbers are grouped.

associative property of addition

$ \color{#16387C}{(a+b)+c=a+(b+c)} $

associative property of multiplication

$ \color{#16387C}{(a \cdot b) \cdot c=a \cdot (b \cdot c)} $

asymptote

On a graph, a line which is approached by a curve but never reached.

atom

A basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons.

atomic mass

The mass of an atom, most often expressed in unified atomic mass units.

atomic number

The number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus.

attribute

A characteristic to describe an object usually within a pattern. The attribute usually refers to the shape, size, or color.

average

A number that represents the characteristics of a data set, calculated by adding a group of numbers then dividing by the number of elements in that group.

axiom

A basic assumption about a mathematical system from which theorems can be deduced. For example, the system could be the points and lines in the plane. Then an axiom would be that given any two distinct points in the plane, there is a unique line through them.

axis

The horizontal and vertical lines that form the quadrants of the coordinate plane. The horizontal axis is usually called the x-axis, the vertical axis is usually called the y-axis.

axis of symmetry

A line that passes through a figure in such a way that the part of the figure on one side of the line is a mirror reflection of the part on the other side of the line.