Cardinal numbers

You already know cardinal numbers 1 through 1000. Of the cardinal numerals only один changes it's ending to agree with the noun (один карандаш, одна ручка, одно письмо, одни брюки) and два changes it's form to agree with the feminine nouns (две книги).

Ordinal numerals
Ordinal numerals function like adjectives: they agree with their head word (noun or pronoun) in gender, number and case. They function like English numbers first, second, third, etc. Here is the list of ordinal numbers 1-10.

Click each ordinal number to listen. Repeat the numbers, imitating their pronunciation. Note vowels reduction.

• Adjectives spelling rules apply to ordinal numbers. For example, if an adjective has end stress, it's masculine form ends on -ой (второй, -ая, -ое, -ые).
• You must memorize feminine, neuter and plural endings for the word третий (третья, третье, третьи). It is a soft stem adjective, but it's endings are slightly different from regular soft stem adjective endings (-ья, -ье, -ьи instead of -яя, -ее, -ие).

• Ordinal numbers 11-20 are not difficult to memorize if you have learned the corresponding cardinal numbers 11-20. They are very much the same. You should simply replace -ь with the appropriate adjective ending. Compare: 

   

  Cardinal	Ordinal
  одиннадцать	одиннадцатый (-ая, -ое, -ые)
  двенадцать	двенадцатый (-ая, -ое, -ые)

Compound ordinal numbers 

Compound ordinal numbers are formed by placing simple numbers in sequence. But only a final component of a compound ordinal numeral is an ordinal. The rest are cardinals. Here are some examples of compound ordinal numbers:

• When talking about years, there is no way to say "nineteen seventeen" or "nineteen ninety one" in Russian. You have to say the whole sequence of numbers, and the last number in that sequence must be ordinal (it is like saying one thousand nine hundred seventeenth year  for "the  year of 1917").