Declining Small Numbers
When counting objects as the subject of a sentence (Nominative case), the numbers 2, 3, and 4 take a noun in the Genitive singular.
However, in oblique cases (any case other than Nominative or inanimate Accusative), the number declines, and the noun switches to the plural form of that required case. Notice that in all oblique cases, the gendered forms два and две merge into a single form for all genders.
The Genitive and Prepositional Cases
The Genitive and Prepositional forms for these numbers are identical. They all end in -х.
| Number | Genitive / Prepositional |
|---|
| 2 | двух |
| 3 | трёх |
| 4 | четырёх |
You will use the Genitive case after prepositions like от (from), из (out of), or для (for).
You will use the Prepositional case after prepositions like в (in) or на (on) when describing location, or о (about).
The Dative Case
The Dative forms for these numbers all end in -м.
| Number | Dative |
|---|
| 2 | двум |
| 3 | трём |
| 4 | четырём |
Use the Dative case for indirect objects (such as who you are delivering something to) or after prepositions like к (towards) and по (around / distributed across).
The Instrumental Case
The Instrumental forms end in -мя.
| Number | Instrumental |
|---|
| 2 | двумя |
| 3 | тремя |
| 4 | четырьмя |
Use the Instrumental case with the preposition с to describe doing something "together with" or "alongside" multiple people or objects.