Decimal : A decimal is a number represented by digits in front and after a decimal point. In front of the decimal point the digits are the ones digit, tens digit, hundreds digit and so on. After the decimal point there are the tenths digit, hundredths digit, thousandths digit and so on. For example the decimal 1.3 can be written as $1\frac{3}{10}.$

Even : Even can refer either to an even function or an even number.

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 $\frac{3}{2}.$

Rational number : A rational number is a number of the form $\frac{a}{b}$ with integers $a, b.$

Square root : The square root of $x$ denoted by $\sqrt{x}$ is the positive number such that $(\sqrt{x})^2=\sqrt{x}\cdot \sqrt{x}=x.$ For example $\sqrt{9}=3.$

Whole number : A whole number is any of the numbers $0,1,2,\ldots.$

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 $x.$

Inequality : An inequality is a statement that contains an inequality sign between two expressions.

Inequality sign : The word inequality sign refers to any of $\lt,$ $\gt,$ $\leq$ and $\geq.$

Negative : A number is negative if it is $\lt 0.$

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

Factor : If a natural number is divisible by a second natural number, that second natural number is called a factor of the first natural number. For example the factors of 12 are 1,2,3,4,6 and 12.

Greatest common factor : The greatest common factor of two natural numbers $m$ and $n$ is a natural number $k$ that is a factor of $m$ and $n$ such that there is no bigger number that is also a factor of $m$ and $n.$ For example the greatest common factor of 12 and 15 is 3. To simplify a fraction one can divide both the numerator as well as the denominator by the greatest common factor of the numerator and the denominator. The exponents in the prime factorization of the greatest common factor of two numbers are the minima of the exponents in the prime factorization of the two numbers.

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