Understand what a ordinal number It is not a complicated task at all, there being no more theory to learn about it, with a simple specification anyone should get the idea well. In itself, the number that shows the exact position of any kind of element within a given set is called ordinal. This serves to give good succession to the elements presented in the mentioned set, having a respected order, reaching the possibility that they are infinite.
For example, it is like saying that the first number (1) goes before the second (2), that the second is located before the third (3), that the third is positioned before the fourth (4) and that this will go before the fifth (5) in position, to give a notorious example, and so on ad infinitum.
As said, remember that language allows us to refer to infinite numbers of ordinal type.
So let's learn from 1 to 20 how ordinal numbers are written:
1st = First
2nd = Second
3rd = Third
4th = Fourth
5th = Fifth
6th = Sixth
7th = Seventh
8th = Eighth
9th = Ninth
10th = Tenth
11th = Eleventh
12th = Twelfth
13th = Thirteenth
14th = Fourteenth
15th = Fifteenth
16th = Sixteenth
17th = Seventeenth
18th = Eighteenth
19th = Nineteenth
20th = Twentieth