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1.4

# Glossary

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## Symbols

$$\exists$$ :There exists.

$$\in$$: Belongs to

$$\forall$$: For every

$$\mathbb N$$: The set of natural numbers $$0,1,2,3,…$$

$$\mathbb Q$$: The set of rational numbers.

$$\mathbb R$$: The set of real numbers.

$$\mathbb Z$$: The set of integer numbers $$…,-3,-2,-1,0, 1,2,3,…$$

## I

Integer: a number of the set $$\mathbb Z=\lbrace …,-3,-2,-1,0,1,2,3,…\rbrace$$

## N

Natural number: a number of the set $$\mathbb N=\lbrace 0,1,2,3,…\rbrace$$

## R

Rational number: a number of the set $$\mathbb Q=\lbrace …\frac ab:\, a\in\mathbb Z, b\in\mathbb N\rbrace$$

Real number: an element of $$\mathbb R$$. The set $$\mathbb R$$ contains the limits of sequences of rational numbers and elements like square roots, $$\pi, e,…$$

## S

Square root of $$x\ge 0$$: the positive number $$y$$ satisfying $$y^2=x$$.

$$m-$$th square root of $$x\ge 0$$: the positive number $$y$$ satisfying $$y^m=x$$.