Instrumental Case: Basic Rules
The table below represents basic endings of the instrumental case:
| Gender | Singular | Plural |
|---|---|---|
| Masculine | -ом / -ем / -ём | -ами / -ями |
| Feminine | -ой / -ей / -ёй / -ью | |
| Neuter | -ом / -ем / -ём |
These endings are added to the stem of nouns, which is formed by dropping the nominative singular endings.
In singular, the ending -ем (for masculine and neuter nouns) is used when the ending is not stressed for the following groups of nouns:
- Soft stem nouns
- Nouns with a stem ending in ж, ц, ч, ш, щ. These nouns undergo spelling rule #3.
In singular, the ending -ём (for masculine and neuter nouns) is used for soft stem nouns if the ending is stressed.
In singular, the ending -ей (for feminine nouns) is used when the ending is not stressed for the following groups of nouns:
- Soft stem nouns ending in -я
- Nouns with a stem ending in ж, ц, ч, ш, щ. These nouns undergo spelling rule #3.
In singular, the ending -ью (for feminine nouns) is used for soft stem nouns ending in -ь (soft sign).
In plural, the ending -ями (for all genders) is used for soft stem nouns. However, some nouns may undergo the spelling rule #2 and they will have the ending -ами (e.g. ночь - ночами)