Besides the ordinary descriptive adjectives, Russian has a special class of possessive adjectives built straight from nouns: ма́мин ("mum's"), Ма́шин ("Masha's"), ли́сий ("fox's, vine"). They answer чей? ("whose?") and express belonging or origin not with a genitive noun but with a true adjective that agrees with the thing possessed. English does something similar with boy's / dog's, but those are clitics, not full adjectives; Russian inflects these forms for gender, number, and case like any modifier. There are two families — the -ин/-ов type from people, and the -ий/-ья/-ье type from animals — and each has its own slightly irregular ("mixed") declension. They carry a warmer, more colloquial, or more idiomatic colour than the neutral genitive, and they live on inside dozens of fixed expressions.
The -ин / -ов type: from people and names
These are formed from nouns denoting people — especially family members and first names (the affectionate, diminutive kind). Add -ин to a stem ending in -а/-я, -ов/-ев to other masculine names:
| Noun | Possessive | Meaning |
|---|---|---|
| ма́ма | ма́мин | mum's |
| па́па | па́пин | dad's |
| ба́бушка | ба́бушкин | grandma's |
| де́душка | де́душкин | grandpa's |
| Ма́ша | Ма́шин | Masha's |
| сестра́ | сестри́н | sister's |
The nominative looks like a short form (ма́мин, ма́мина, ма́мино, ма́мины) — bare masculine, -а feminine, -о neuter, -ы plural — and it agrees with the possessed noun, not the possessor:
Э́то ма́мина су́мка.
This is mum's bag. — су́мка is feminine, so ма́мина (agreeing with 'bag', not with 'mum').
Где па́пин телефо́н?
Where's dad's phone? — телефо́н is masculine, so the bare masculine па́пин.
Мы пое́дем на де́душкину да́чу.
We'll go to grandpa's dacha. — accusative feminine да́чу → де́душкину.
The mixed declension
Here is the quirk: this type declines with a mix of noun-like and adjective-like endings. The nominative and accusative use noun endings (short-form-style: ма́мин, ма́мина), but the oblique cases switch toward the regular adjective endings:
| Case | Masc. | Fem. | Neut. | Plural |
|---|---|---|---|---|
| Nom. | ма́мин | ма́мина | ма́мино | ма́мины |
| Gen. | ма́миного | ма́миной | ма́миного | ма́миных |
| Dat. | ма́миному | ма́миной | ма́миному | ма́миным |
| Instr. | ма́миным | ма́миной | ма́миным | ма́миными |
| Prep. | (о) ма́мином | (о) ма́миной | (о) ма́мином | (о) ма́миных |
Я взял ключи́ из ма́миной су́мки.
I took the keys out of mum's bag. — genitive feminine ма́миной, an adjective-type ending.
Мы говори́ли о Ма́шиных пла́нах.
We were talking about Masha's plans. — prepositional plural Ма́шиных.
The -ий / -ья / -ье type: from animals
The second family is built from animals (and a few people-related stems) and is hugely productive in fixed and figurative expressions. The masculine nominative ends in -ий, but the giveaway is the soft sign -ь- that appears in the feminine -ья, neuter -ье, plural -ьи, and right through the oblique cases:
| Animal | Masc. | Fem. | Neut. | Plural |
|---|---|---|---|---|
| лиса́ (fox) | ли́сий | ли́сья | ли́сье | ли́сьи |
| волк (wolf) | во́лчий | во́лчья | во́лчье | во́лчьи |
| медве́дь (bear) | медве́жий | медве́жья | медве́жье | медве́жьи |
| соба́ка (dog) | соба́чий | соба́чья | соба́чье | соба́чьи |
| пти́ца (bird) | пти́чий | пти́чья | пти́чье | пти́чьи |
| ры́ба (fish) | ры́бий | ры́бья | ры́бье | ры́бьи |
The oblique forms carry the -ь- throughout: gen. masc./neut. ли́сьего, dat. ли́сьему, instr. ли́сьим, prep. ли́сьем; fem. gen./dat./instr./prep. ли́сьей, acc. ли́сью; plural gen./prep. ли́сьих, dat. ли́сьим, instr. ли́сьими. In other words, this is the regular soft-stem adjective declension with a -ь- written before each ending.
Мы нашли́ ли́сью нору́ у реки́.
We found a fox's den by the river. — accusative feminine ли́сью with the soft sign.
Соба́ка маха́ла хвосто́м, как лиса́, — ли́сьего ра́зве что не хвата́ло.
The dog wagged its tail like a fox — only a fox's [tail] was missing. — genitive ли́сьего.
На обе́д был суп из ры́бьих голо́в.
There was soup made from fish heads for lunch. — genitive plural ры́бьих.
Fixed and figurative phrases
This is where the animal type really earns its keep — it's locked into many idioms, often metaphorical:
| Phrase | Literal | Meaning |
|---|---|---|
| Бо́жья коро́вка | God's little cow | ladybird / ladybug |
| медве́жья услу́га | a bear's favour | a well-meant act that does harm |
| во́лчий аппети́т | a wolf's appetite | a ravenous appetite |
| пти́чье молоко́ | bird's milk | something wonderful but unobtainable (also a cake) |
| ры́бий жир | fish fat | cod-liver oil |
Не помога́й ему́ так — э́то медве́жья услу́га.
Don't help him like that — it's a well-meant disservice. — медве́жья услу́га, a set phrase.
По́сле похо́да у нас был про́сто во́лчий аппети́т.
After the hike we had an absolutely ravenous appetite. — во́лчий аппети́т.
Possessive adjective vs the genitive of possession
For "mum's bag" Russian also allows the plain genitive of the possessor: су́мка ма́мы (literally "the bag of mum"). So which do you choose? The difference is one of register and nuance, not strict grammar:
- Possessive adjective (ма́мина су́мка): warmer, more colloquial, and the natural choice with close family and first names. It also comes before the noun, like any adjective.
- Genitive (су́мка ма́мы): more neutral and the default when the possessor is itself modified, a longer phrase, or not a person — and it follows the noun. You cannot make a smooth possessive adjective from most full nouns (you'd never say *учи́тельина кни́га for "the teacher's book"; you say кни́га учи́теля).
Э́то ма́мина маши́на, а та — маши́на сосе́да.
This is mum's car, and that one is the neighbour's car. — adjective for 'mum' (close family), genitive сосе́да for 'neighbour'.
The genitive of possession is covered in full on the genitive: possession and 'of'.
How this differs from English
English has a single possessive clitic 's (mum's, the fox's, the teacher's) that attaches to almost any noun and never changes. Russian splits the job: a productive but restricted set of true adjectives (only from people and animals, mostly informal) versus the all-purpose genitive noun. The crucial mental shift is that ма́мин is not "mum + 's" — it is a full adjective that agrees with the possessed thing: ма́мин телефо́н but ма́мина су́мка but ма́мино пальто́, exactly as но́вый/но́вая/но́вое would. English speakers reliably forget to inflect it.
Common Mistakes
❌ Э́то ма́мин су́мка.
Incorrect — the possessive agrees with су́мка (feminine), so ма́мина, not the masculine ма́мин.
✅ Э́то ма́мина су́мка.
This is mum's bag.
❌ Я взял ключи́ из ма́мина су́мки.
Incorrect — the genitive feminine is ма́миной (adjective-type ending), not ма́мина.
✅ Я взял ключи́ из ма́миной су́мки.
I took the keys out of mum's bag.
❌ Мы нашли́ ли́сию нору́.
Incorrect — the animal type takes a soft sign: feminine accusative is ли́сью, not *ли́сию.
✅ Мы нашли́ ли́сью нору́.
We found a fox's den.
❌ учи́телина кни́га
Incorrect — you can't form a possessive adjective from учи́тель; use the genitive кни́га учи́теля.
✅ кни́га учи́теля
the teacher's book
Key Takeaways
- Russian builds possessive adjectives from nouns to answer чей? — they agree with the possessed thing, not the owner.
- The -ин/-ов type comes from people/names (ма́мин, па́пин, ба́бушкин, Ма́шин) and has a mixed declension: nominative/accusative like a short form (ма́мина су́мка), obliques like an adjective (ма́миной су́мки).
- The -ий/-ья/-ье type comes from animals (ли́сий, во́лчий, медве́жий, соба́чий, пти́чий, ры́бий) and carries a soft sign -ь- through the feminine, neuter, plural, and all oblique cases (ли́сья нора́, ли́сьего хвоста́).
- Both survive in fixed phrases: Бо́жья коро́вка ("ladybird"), медве́жья услу́га ("a well-meant disservice"), во́лчий аппети́т.
- They contrast with the genitive of possession (су́мка ма́мы), which is more neutral and the only option for most full nouns.
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- Full Adjective Declension TablesA2 — The complete case-by-case declension of Russian adjectives, for both hard stems (но́вый) and soft stems (после́дний). Masculine and neuter share all oblique forms (gen -ого/-его, dat -ому/-ему, instr -ым/-им, prep -ом/-ем); the feminine collapses genitive=dative=instrumental=prepositional into a single -ой/-ей, with -ую/-юю in the accusative; the plural shares gen=prep -ых/-их, dat -ым/-им, instr -ыми/-ими. The masculine accusative splits by animacy (но́вого студе́нта vs но́вый стол), and the -ого/-его ending is pronounced with a /v/ (но́вого = 'nóvava').
- Adjective Agreement: The BasicsA1 — Russian adjectives agree with their noun in gender, number, AND case. In the nominative the endings are masculine -ый/-ий/-ой (но́вый, ма́ленький, большо́й), feminine -ая/-яя (но́вая, после́дняя), neuter -ое/-ее (но́вое, после́днее), and plural -ые/-ие (но́вые) for all genders. So 'new' is но́вый дом, но́вая маши́на, но́вое окно́, but но́вые кни́ги. Adjectives also change for case (в но́вом до́ме) and normally come BEFORE the noun, as in English.
- Genitive: Possession and 'of'A2 — The genitive's flagship job: expressing both the English possessive ('s) and the preposition 'of' at once. There is no apostrophe and no separate 'of' word — possession is shown purely by putting the owner in the genitive AFTER the thing owned: маши́на отца́ (father's car / the car of the father), центр го́рода (the centre of the city). The whole possessor phrase declines, not just its head.
- Genitive: FormsA2 — The genitive (роди́тельный паде́ж) is one of the most-used and most-varied cases. The singular is tidy: masc/neuter -а/-я (стола́, окна́, музе́я), feminine -ы/-и (кни́ги, неде́ли, но́чи). The plural is the single hardest ending set in Russian — a three-way split between zero ending (often with a fleeting vowel: книг, о́кон, де́вушек), -ов/-ев (столо́в, музе́ев, отцо́в), and -ей (ноже́й, словаре́й, ноче́й). Learn the decision procedure, not a word list.