§ 230. Amongthe ordinals there are also simple, derivative and compound words.
The simple ordinals are first, second and third.
The derivative ordinals are derived from the simple and derivative cardinals by means of the suffix-th:
four-fourth, ten-tenth, sixteen-sixteenth, twenty-twentieth, etc.
Before the suffix -th the final у is replaced byie:
thirty - thirtieth, etc.
Mind the difference in the spelling of the stems in the following cardinals and ordinals:
The compound ordinals are formed from composite cardinals. In this case only the last component of the compound numeral has the form of the ordinal:
twenty-first, forty-second, sixty-seventh, one hundred and first, etc.
§ 231. Numerals do not undergo any morphological changes, that is, they do not have morphological categories. In this they differ from nouns with numerical meaning. Thus the numerals ten (десять), hundred (сто), thousand (тысяча)do not have plural forms:
two hundred and fifty, four thousand people, etc.,
whereas the corresponding homonymous nounsten (десяток), hundred (сотня), thousand (тысяча) do:
to count in tens, hundreds of people, thousands of birds, etc.