Question

What is the ordinal number?

Answer 1

An ordinal number is an adjective derived from a number that describes an object's position in a sequence.

Explanation:

(see here for more detail)

With some exceptions (listed below), ordinal numbers are created by adding -th to the end of a cardinal number (ordinary numbers). For example:
seven `rarr` seventh
six `rarr` sixth

In context: There are ten cards numbered in order. This one has the number 'six' on it. It is the sixth.

Irregular ordinal numbers:
one `rarr` first
two `rarr` second
three `rarr` third
five `rarr` fifth
eight `rarr` eigth
nine `rarr` ninth
twelve `rarr` twelfth