Addition : Addition is the mathematical operation that describes increasing a number by an amount equal to a second number. The mathematical symbol for addition is the plus sign $+.$ The term addition is also used for a generalization of this basic operation on numbers to functions, vectors and matrices.

Count : To count means to find out the number of objects by adding one for every object.

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

Denominator : The denominator of a fraction $\frac{a}{b}$ is the number $b$ below the fraction bar.

Fraction : A fraction is a number that can be written as $\frac{a}{b}$ with an integer $a$ and a natural numbers $b.$ A fraction $\frac{a}{b}$ is the result of the division $a\div b.$ Examples of fractions are $\frac{1}{2}, -\frac{2}{3}$ and $\frac{3}{2}.$

Numerator : The numerator of a fraction $\frac{a}{b}$ is the number $a$ above the fraction bar.

Positive : Positive means $\geq 0.$

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

Cube : A cube is a three-dimensional shape with 6 faces that are all squares. A cube has 8 corners and 12 edges.

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.

Half : A Half is the number equal to $\frac{1}{2}=0.5.$

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

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.

Quarter : One quarter is the number $\frac{1}{4}=0.25.$

Ratio : A ratio is a comparison of two numbers using a division.

Sphere : A sphere is a three-dimensional shape that has a boundary equal to a set of points with a constant distance to a point. The point is called the center of the sphere and the distance is called the radius $r$ of the sphere. The volume of a sphere with radius $r$ is $\frac{4}{3}\pi r^3$ and the surface area is $4\pi r^2.$

Squared : $x$ squared refers to the number $x^2=x\cdot x.$ For example 3 squared equals 9.

Surface area : The surface area of a three-dimensional shape is the area of the surface of the three-dimensional shape. For example the surface area of a cube with edge length 1 $cm$ is 6 $cm^2.$