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), ...

Ordinals numbers tell you what position something is in. You often use them to rank or order things. Most ordinal numbers end with a 'th' sound, like 'fourth' or 'fifth'. However, they can also end ...