The word Number comes from the Latin numĕrus , with the same meaning. It is any sign or symbol used to designate quantities, values or entities that behave as quantities. It is the expression of the relationship between quantity and unit.
Since the beginning of civilization, man has experienced the need to count, thus inventing numbers, as is the case with Roman or Arabic numerals (the Arabs introduced them to Europe), the latter are the most used symbols to represent numbers., which are 1, 2, 3, 4, 5, 6, 7, 8, 9 and 0.
The numbers are grouped into sets or various structures. Each set of numbers includes the previous one, and it is more complete than it and with greater possibilities in its operations.
The set of numbers can be classified into: natural numbers, which are those that we normally use to count, they are positive numbers and without a decimal part (N = 0,1, 2, 3,…). The whole numbers, includes all the natural numbers and their opposites; that is, including the negatives (-2, -1,0, 1, 2,…).
There are also rational numbers, those that can be expressed as a quotient of two whole numbers. The set Q of rational numbers is made up of whole numbers and fractional numbers (in fraction form). The irrational numbers are numbers that have infinite decimal (3.5, 60.2,…).
The real numbers, wrap all the numbers previously described. They cover the real line and any point on it is a real number. The real numbers are not arranged in such a way that they can be ordered one at a time; that is, there is no "next" of a rational number, since between any two rational numbers there are other infinities.
Finally, we have imaginary numbers, those that are produced by extracting the square root of a negative number. And the complex numbers, which are made up of all real numbers and all imaginary ones.
In the field of grammar, a number is a grammatical category that expresses the singularity and plurality of a word. Within the number the singular is distinguished, which designates a single being or object, and the plural, which indicates more than one or a set.
