Genitive singular: Basic Rules

The table below represents basic endings of the genitive singular:

Gender	Endings
Masculine	-а / -я
Feminine	-ы / -и
Neuter	-а / -я

These endings are added to the stem of nouns, which is formed by dropping the nominative singular endings.

The endings -я (for masculine and neuter) and -и (for feminine nouns) are used if the final consonant of the stem is soft (so called soft stem nouns).

According to the spelling rule #1 feminine nouns ending -жа, -чa, -ща, -ша and -ка, -ха, -га can not add the ending -ы. That is why they will have the ending -и in the genitive singular.