Natural numbers

Natural numbers are the ordered set of numbers that humanity has used to count, which are assigned ordinal names to name each particular number:

Units
Number	Ordinal
1	First
2	Second
3	Third
4	Fourth
5	Fifth
6	Sixth
7	Seventh
8	Eighth
9	Ninth

11 to 19
Number	Ordinal
11	Eleventh
12	Twelfth
13	Thirteenth
14	Fourteenth
15	Fifteenth
16	Sixteenth
17	Seventeenth
18	Eighteenth
19	Nineteenth

Tens
Number	Ordinal
10	Tenth
20	Twenty
30	Thirty
40	Forty
50	Fifty
60	Sixty
70	Seventy
80	Eightieth
90	Ninetieth

Hundreds
Number	Ordinal
100	Hundredth
200	Two hundredth
300	Three hundredth
400	Four hundredth
500	Five hundredth
600	Six hundredth
700	Seven hundredth
800	Eight hundredth
900	Nine hundredth

And so we could continue listing them until we get bored, since the set of natural numbers is infinite

However, there is no universal agreement on whether zero should be considered a natural number. Historically, 0 as a number had a much later origin than the rest of numbers. The Babylonians, in the 7th century BC. they had a symbol for zero, but just to leave no gaps when representing quantities in their base 60 positional numbering system in cuneiform script

The Hindu mathematician Brahmagupta, already considered it a number more, in the 7th century; and possibly, the Olmec and Mayan civilizations already used it as a number, centuries earlier. On the other hand, the Greeks, from which the mathematics of Western culture derive, had no concept of zero; and for that reason, there is no way to represent it in Roman numerals, a culture that drank from Greek, which prevailed in Europe until the base 10 decimal system (of Indian origin and adopted by the Arabs) began to slowly prevail from the 13th century onwards

For this reason, you can define natural numbers in two ways:

\begin{cases}\mathbb{N}=\{1,2,3,4,5,\cdots,n\} & \text{(if we do not include 0) } \\ \mathbb{N}_0=\{0,1,2,3,4,5,\cdots,n\} & \text{(if we do include 0) } \end{cases}