A Cardinal Number is a number that says how many of something there are, such as one, two, three, four, five. An Ordinal Number is a number that tells the position of something in a list, such as 1st, …

In this case we refer to 7 as an ordinal number, or simply ordinal. Hence, ordinal numbers carry more information than cardinal num-bers, namely order in addition to size.

90 = ninety 100 = one hundred 101 = one hundred (and) one 1,000 = one thousand 1,001 = one thousand (and) one 1st = first 2nd = second 3rd = third 4th = fourth 5th = fifth 6th = sixth 7th = …

We only care about the order of points in the ordinal, so two subsets ordered in the "same way" count as the same ordinal. For example, f0; 1; 2g and f 37; 3; g count as the same ordinal.

Oct 9, 2024 · Ordinal letters are the suffixes after the numeral (th, st). In general, treat ordinals the same as regular numbers: Spell out “first” through “ninth,” and use numerals for “10th” and above.

Ordinal Numbers (1 – 100) 1 → 1st (first) 2 → 2nd (second) 3 → 3rd (third) 4 → 4th (fourth)

For the next two sections, we want to move away from thinking about cardinality and toward thinking about ordinal notions. The notion of cardinality concerns only the size of a set.