The decimal numbers They are those that have a decimal part and therefore are opposed to integers, which are a generalization of natural numbers, which includes negative integers and zero; whole numbers do not have a decimal part.
Within the decimal numbers we find, on the one hand, with the rational numbers, which can be expressed through a fraction of two whole numbers and on the other hand with the irrational numbers, when they cannot be represented by a fraction of two whole numbers.
But also, within the rational numbers we find another division, between exact decimal numbers (when they have a number of finite decimal places) and repeating decimal numbers (when they have a periodic part that can be repeated indefinitely 10,3333). And in the periodic decimal numbers we also find a distinction, with cigars, if the decimal part is made up of a period that repeats indefinitely; or with mixed, if there is a mix between the non-periodic part and the periodic part in the decimal part.
In the Spanish language, currently, there are three basic ways of notation of decimal numbers and that has to do precisely with the sign used as a decimal separator.
The decimal point (3.14) is the most used way at the behest of electronic calculators and computers, it is unusual for it to be used in handwritten annotations; the decimal point (3,14) is the most used form in publications and handwritten annotations; and the decimal apostrophe (3'14), is usually used in handwritten entries.
