Numerals

With this post we start our discussion, dedicated to a notoriously tricky item in Russian: the numerals. 

There are three main classes of numerals in Russian: 

Cardinal

Ordinal

Collective 

Cardinal numerals indicate quantity and is used in counting. For example, один (one), пять (five), двадцать три (twenty-three).

An ordinal number indicates the position of an item in a sequence, such as первый (first), второй (second) or третий (third).

A collective numerals denotes a number of persons or things considered as one group or whole.

The bad news is that all three classes decline. Moreover, use of numerals in context drives the vast majority of Russian learners bananas.

The Old Slavonic had three numbers:

Singular (1)

Dual (paucal numerals 2, 3, 4)

Plural (≥ 5).

The numerals 2,3,4 took a noun in an archaic dual case that defuncted in XVI century. Dual case merged with the genitive SINGULAR case, that's why the numeral syntax is very complex in Russian.

For nominative (and inanimate accusative) nouns, the following rule is used to select the proper form of the item:

1 --> noun in the nominative case
2, 3, 4 --> noun in the genitive singular
5 and more --> noun in the genitive plural

Keep in mind the numerals 2, 3, 4 themselves are either in the nominative or inanimate accusative.

Cardinal numeral 1:

1) The numeral один (1) should be used in the proper form to indicate gender:

 masculine --> один, 

feminine  --> одна,   

neuter --> одно. 

E.g., В этой семье один сын (m), одна дочка (f), одно домашнее животное (n).

2)  The numeral один (1) should be used in the same case as a noun.

Один  охотник (Nom) убил одного зайца (Accu animate = genitive) одним выстрелом (Instrumental).

3)  Numeral один changes its form to agree with number (believe it or not!) of the modified noun.

 It means it has a special plural form одни for nouns used in plural only.

 One can argue that it is a bit illogical as number "one" implies the singular form.  Hmm, Russian is not so crazy ;) We use plural form одни with words that are used in plural only. So far as a noun is in a plural form (though it denotes one item), the modifier (number "one" in this case) should also be in plural form, e.g.,

Одни ножницы = one scissors,

Одни джинсы = one [pair of] jeans.

Cardinal numeral :

Of the cardinal numerals only один changes it's ending to agree with the noun (один дом (m), одна собака (f), одно письмо (n), одни брюки (plural))

and два changes it's form to agree with the feminine nouns (две книги (plural), две чашки (plural)).