If we assume that the Masculine form of such nouns has the feature settings [+Feminine, +Masculine], Russian requires a feature value switch which toggles this setting to [+Feminine, -Masculine] in order to fully semantically specify Feminine correlates. Notice that this characterization also fits nouns which are exclusively Feminine, which are not susceptible to derivation, such as
sestra 'sister',
mat' 'mother. It also predicts a class of exclusively Masculine nouns, [-Feminine, +Masculine]. Such nouns are found in the language, e.g.
brat 'brother',
otec 'father'. Interestingly, it also predicts a class of nouns which are neither Feminine nor Masculine but for whom Gender is relevant. This class is also found in Russian and other Slavic languages:
tjulen' 'seal',
sobaka 'dog', etc. are not specified for (Natural) Gender but are animate. Beard (
1996) argues that these nouns have precisely this designation and, moreover, animacy is not a category in Slavic languages, but rather a peripheral function of Natural Gender.