The dual in Slavic languages

Common Slavic had a complete singular-dual-plural number system, although the dual paradigms showed considerable syncretism. Verbs had the same form in the second and third person dual; however, nouns, adjectives, and pronouns inherited the three Proto-Indo-European dual forms.^[1] Proto-Slavic is the proto-language from which Old Church Slavonic and all the other Slavic languages later emerged. ... In linguistics, syncretism is the agreement in form of distinct morphological forms of a word. ...

Of the living languages, only Slovene and Sorbian have preserved the dual number as a productive form. In all of the remaining languages, its influence is still found in the declension of nouns of which there are commonly only two: eyes, ears, shoulders, in certain fixed expressions, and the agreement of nouns when used with numbers.^[2] The Sorbian languages are classified under the West Slavic branch of the Indo-European languages. ...

In all the languages, the declension of the "two" maintains most of its dual characteristics, which can be verified from the table below.

Notes:

1. In Polish, there is a further distinction between animate and inanimate masculine nouns. For animate masculine nouns, the possible nominative forms are dwaj, dwoch, or dwu.
2. In Serbian/Croatian and Sorbian, the form given is only for the genitive case; the locative case is then the same as the dative or instrumental cases.

The words oba and obidva meaning "both" are declined similarly to the numeral "two."

In Common Slavic, the rules where relatively simple for determining the appropriate case for the noun, when it was used with a numeral. The following rules apply:

1. With the numeral "one", both the noun, adjective, and numeral were in the same singular case, with the numeral being declined as an adjective.
2. With the numeral "two", both the noun, adjective, and numeral were in the same dual case. There were separate forms for the masculine and neuter-feminine nouns.
3. With the numerals "three" and "four," the noun, adjective, and numeral were in the same plural case.
4. With any numeral above "four", in the nominative case, the numeral was followed by the noun and adjective in the genitive plural case. For all other cases, both the noun, adjective, and numeral were in the same plural case.

With the loss of the dual in most of the Slavic languages, the above pattern now is only seen in the forms of the numbers for the tens, hundreds, and rarely thousands. This can be seen by examining the following table:

In those languages that lost the dual, the above rules become the following for all languages except Bulgarian and Macedonian, which have lost all declensions:^[4]

1. With the numeral "one", both the noun, adjectives, and numeral are in the same singular case, with the numeral being declined as an adjective.
2. With the numerals "two", "three" and "four", there are two different possibilities. In Polish, Czech, Slovak, Sorbian, and Ukrainian, the numeral, adjective, and noun are in the same nominative plural case. In Ukrainian, the stress on the noun is that of the genitive singular (or the old dual). In Russian, Belarusian, and Serbo-Croatian, the genitive singular is used for the noun, which in most cases resembles the dual in form is used. The adjective can be either in the genitive singular or plural forms. In all other cases, the appropriate plural form is used.
3. With the numerals "five" and above, in the nominative case, the numeral is followed by the noun and adjectives in the genitive plural case. For all other cases, both the noun, adjectives, and numeral are in the same plural case.

The resulting changes can be seen in the table below where the word "wolf" is used to form nominative noun phrases with various numerals.

The dual has also left traces in the declension of nouns describing those object which humans customarily had two of, for example: eyes, ears, legs, breasts, and hands. Often the plural declension is used to give a figurative meaning. The table below summarises the key such points. This article or section does not cite its references or sources. ...

Slovene

The Slovene language is the only major Slavic language that retains full grammatical use of the dual, including distinct dual forms for both nouns and verbs. The dual declension merges with the plural in certain nominal cases (e.g., genitive). Note that dual number is compatible with use of the pronoun oba(dva) or obe(dve) ("both"). This article needs cleanup. ...

Nominative case of noun "wolf", with and without numerals:

The dual is recognised by many Slovene speakers as one of the most distinctive features of the language and a mark of recognition, and is often mentioned in tourist brochures.

For verbs, the endings in the present tense are given as -va, -ta, -ta. The table below shows a comparison of the conjugation of the verb oddati, which means to give away and belongs to Class I in the singular, dual, and plural.

In the imperative the endings are given as -iva for the first person dual and -ita for the second person dual. The table below shows the imperative forms for the verb hoditi (to walk) in the first and second persons of the imperative.