A Handbook of the English Language
Chapter 100
THE CARDINAL NUMBERS.
ยง 261. Generally speaking, the greater part of the cardinal numbers are undeclined. As far as _number_ goes, this is necessary.
_One_ is naturally and exclusively _singular_.
_Two_ is naturally _dual_.
The rest are naturally and exclusively _plural_.
As to the inflection of gender and case, there is no reason why all the numerals should not be as fully inflected as the Latin _unus, una, unum_, _unius_. It is a mere habit of our language that they are not so in English.
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