Division : Division is the mathematical operation that divides objects equally into groups. More generally $x\div y$ is defined as the number that if multiplied by $y$ equals $x.$

Equation : An equation is a mathematical statement in which two expressions are written with an equal sign in between. A solution of an equation is a set of variables that makes the statement a true statement.

Solution : A solution to an equation is a choice of variables that when substituted into the equation results in a true statement.

Subtraction : Subtraction is the mathematical operation that describes decreasing a number by an amount equal to a second number. The mathematical symbol for subtraction is the minus sign $-.$ The term subtraction is also used for a generalization of this basic operation on numbers to functions, vectors and matrices.

Centimeter : A centimeter ($cm$) is $\frac{1}{100}$ of a meter.

Circle : A circle is a two-dimensional shape. The boundary of a circle is a set of points that has the same distance (the radius) from the center of the circle.

Circumference : The perimeter of a circle is called circumference. The length of the circumference $C$ can be calculated as $C=2\pi r=\pi d,$ where $r$ is the radius and $d$ the diameter of the circle. This means that the circumference of a circle with diameter 1 $cm$ (radius 0.5 $cm$) is about 3.14 $cm.$

Diameter : The diameter of a circle is the length of a line segment from the boundary of a circle through the center of the circle to the boundary on the other side of the circle.

Pi : Pi or $\pi$ is an irrational number approximately equal to 3.14 that is defined as the quotient of the circumference and the diameter of a circle.

Radius : In a circle or sphere the radius is the distance between the center and the boundary.

Maximum : The maximum of a set of numbers is the highest of the numbers in the set. A function has a maximum at $x_0$ if $f(x_0)\geq f(x)$ for all $x.$

Minimum : The minimum of a set of numbers is the lowest of the numbers in the set. A function has a minimum at $x_0$ if $f(x_0)\leq f(x)$ for all $x.$

Minus : Minus is either a symbol or another word for subtraction.

Number : A number $x$ is a mathematical symbol representing a quantity.

Range : The range of n numbers is the difference between the largest and the smallest number. The range of a function $f$ is the set of all possible values $f(x).$ For example the range of the function $f(x)=x^2$ is the interval $[0,\infty).$