This is one of those quirky grammar rules that can be confounding because the rule for speaking differs from the rule for writing. Ordinal numbers show order, or a position in a series: first (1st), ...

First, second, third... twenty-ninth... In this session we're looking at the meaning, use and spelling of ordinal numbers. We'll meet a very disorganised man, and listen to 6 Minute Vocabulary! 0 / 14 ...