Numerals form a closed class
Recall that a word class is said to be closed if no more words can be added to the class. Whilst in theory it is possible to keep counting to infinity, in practice there are a limited number of numerals that are used to enable this counting process. Numerals are, therefore, categorized as a closed word class (like auxiliary verbs, determiners, pronouns, prepositions, and conjunctions).
Numerals are divided into just two types:
These specify numeric quantity, e.g.
five… [and so on]
Example utterances that incorporate cardinals include the following.
I’ll have two of those, please
he ran around the track four times
you’ve got one more chance
These numerals specify the order of items, e.g.
fifth… [and so on]
Here are some examples of their use.
right, that’s the first button sewn on
Steve came second in his race
take down your tree on twelfth night