In English when we count something we change the ending of its name:
one question |
two questions |
three questions |
This is done in Russian too, but in a slightly more complex way. It looks like this:
оди́н вопро́с | one question |
два вопро́са | two of question |
три вопро́са | three of question |
четыре вопро́са | four of question |
пять вопро́сов | five of questions |
шесть вопро́сов | six of questions |
Notice how the word “вопрос” changes:
One: nominative case and singular
A few (2—4): genitive case (but still singular!)
Many (5 or more): genitive plural
If a number is pronounced as multiple words, only the last part determines the number and case of the noun:
два́дцать оди́н вопро́с | twenty one questions |
два́дцать два вопро́са | twenty two questions |
два́дцать три вопро́са | twenty three questions |
два́дцать четы́ре вопро́са | twenty four questions |
два́дцать пять вопро́сов | twenty five questions |
один—the number one has gender and (astonishingly) a plural form which is used with plural-only nouns. Один is declined like этот:
У меня́ есть оди́н вопро́с. |
I have one question. |
У меня́ есть одна́ кни́га. |
I have one book. |
У меня́ есть одни́ ча́сы. |
I have one clock. |
Я ви́жу одну́ ко́шку. |
I see one cat. |
Я ви́жу одного́ челове́ка. |
I see one man. |
два, две—the number two has gender, but no plural form. It also has an animate accusative form:
У меня́ есть два вопро́са. |
I have two questions. |
У меня́ есть две кни́ги. |
I have two books. |
Я ви́жу двух люде́й. |
I see two men. |
три, четыре—the numbers three and four have an animate accusative form:
Я ви́жу трёх люде́й. | I see three men. |
Я ви́жу четырёх люде́й. | I see four men. |
As a beginner you can get by just using nominative and accusative phrases counting phrases as shown above. But should know that counting phrases in other cases are used, particularly in written Russian.
When counting years we switch from the word “год” to “лето” when we switch to the genitive plural:
Мне четы́ре го́да. | I am four years old. |
Мне пять лет. | I am five summers old. |