Ordnungszahlen

Ordinal numbers ("first, second, third") are adjectives in Russian. They take the same endings as но́вый and agree with their noun: пе́рвый день, пе́рвая неде́ля, пе́рвое ма́я, пе́рвые шаги́.

6th to 10th: шесто́й, седьмо́й, восьмо́й, девя́тый, деся́тый.

Three things to watch

• Stress on the ending: второ́й, шесто́й, седьмо́й, восьмо́й take -о́й in the masculine, like большо́й.
• Тре́тий is special: it has a soft sign before the ending: тре́тья "third (f)", тре́тье, plural тре́тьи.
• Long numbers: only the last word becomes an ordinal: два́дцать пе́рвый век - "the twenty-first century".

Floors, classes and kings

Russia counts floors from the ground: the ground floor is пе́рвый эта́ж, so a British "first floor" is второ́й эта́ж. Мы живём на тре́тьем этаже́ - "We live on the third floor" (two flights up). School years work the same way: Она́ в пе́рвом кла́ссе - "She's in year one."

Monarchs take ordinals as in English, but without "the": Пётр Пе́рвый is "Peter the First", written Пётр I. In writing, ordinals are abbreviated with the ending: 1-й, 2-я, 3-е.

Dates use the neuter, because the word behind them is число́ (date): Сего́дня пе́рвое ма́я. More on that in the topic on dates and age.