The Genitive Plural of nouns in Russian is the most complex case to form. There are many rules (and many exceptions), which I haven't found fully listed anywhere. Therefore, I try to give here a comprehensive list, along with examples.
In nouns having the same stem for the singular and plural (other than accent), the Genitive Plural is generally based on the Nominative Singular. However, in nouns with a different plural stem (irregular plurals) it is based on the Nominative Plural and formed a bit differently.
* Other than the regular correlation between gender and Nominative Singular ending.
|Nominative Singular ends in …||Genitive Plural ending||Example|
|Hard consonant or й||-ов||стол → столов table, m.|
|Soft consonant or sibilant (ш ж щ ч)||-ей||дверь → дверей door, f.
врач → врачей doctor, m.
|Any vowel||null ending (remove the vowel)||книга → книг book, f.
слово → слов word, n.
Exceptions: a few hard-consonant stems take the null ending instead of -ов, resulting in the Genitive Plural being identical to the Nominative Singular.
Many vowel stems in which the last consonant is soft also take -ей instead of the null ending.
A few (neuter) nouns in -ье/-ьё take -ьев/-ьёв rather than the null ending, which would have resulted in -ий/-ей respectively.
|soft consonant + vowel||a soft sign remains||неделя → недель week|
|vowel + soft vowel||the last vowel is replaced with -й||здание → зданий building|
|ь + unaccented vowel||both are replaced with -ий||печенье → печений cookie (analogous to the above case)|
Fleeting vowels may appear in Russian whenever the null ending is used. This occurs also in the Nominative Singular - but isn't a problem since this is the dictionary form of the noun - and in short-form masculine adjectives. In the latter case the rules are similar to those of the Genitive Plural, but not identical.
The correct use of fleeting vowels encompasses two questions:
Exceptions: a handful of nouns use ё or и instead
(I've encountered the claim that ё is generally inserted and just becomes е when unaccented, but accented е also occurs, and I haven't found enough examples overall to generalize).
* I've found no explicitly stated rule regarding this; the following conclusions are based on the results of online morphological analysers. Location of accent and perceived ease of pronunciation seem not to play a part.A fleeting vowel generally appears if and only if the final consonant is к, л, н, ц (including soft counterparts):
|туфля → туфель shoe||утро → утр morning|
|кольцо → колец ring||лекарство → лекарств medicine|
|кукла → кукол doll||ведьма → ведьм witch|
|весна → вёсен spring (season)|
Exceptions: rarely, a fleeting vowel doesn't appear before the above consonants.
In a quite a few nouns, however, a fleeting vowel does appear before б, г, м or р, though this is still the minority of cases.
As mentioned above, the Genitive Plural is based on the plural stem if that differs from the singular. Therefore, this section always specifies the Nominative Plural in addition to the Nominative Singular and Genitive Plural.A sizeable group of nouns form their Nominative Plurals with the ending -ья. These have special rules:
The following classes of nouns always form the Genitive Plural with the null ending:
|Class||Nom. Sg.||Nom. Pl.||Gen. Pl.||English||Comments|
|Neuters in -мя (н-stems)||имя||имена||имён||name||Here the stem in -мен is also used in the singular cases other than the Nom./Acc.|
|Young of animals or humans in -ёнок||котёнок||котята||котят||kitten||From кот cat|
|Nationality, origin or social class in -нин||гражданин||граждане||граждан||citizen||The plural stem ends in a hard н (e.g. the Dative Plural is гражданам).|
This also pertains to most other nouns in -ин, which are somewhat irregular.
Otherwise, the Genitive Plural ending is difficult to predict - including pluralia tantum (nouns with only plural forms), where it is possibly based on a historical singular form. The null ending seems to be the predominant one, though.
The alphaDictionary Website (Site Contents)
George Mitrevski's Russian Grammar Tutorials (Tutorials Index.)
Morphology: Russian Wiktionary and online versions of Zaliznyak's Grammatical Dictionary (links at bottom)