English possessives are frozen little words: my book, my books, my sister, with my sister — my never changes shape no matter what follows. Russian possessives behave like the exact opposite. They are adjectives in disguise: мой, твой, наш and ваш agree with the noun they sit in front of in gender, number and case, exactly as a normal adjective would. The catch that trips up every beginner is what they agree with — not the person who owns the thing (the possessor), but the thing being possessed. This page covers the four agreeing possessives; the non-agreeing his/her/their (его́, её, их) and the reflexive свой each get their own page.
They agree with the possessed noun, not the owner
In English, "his book" tells you the owner is male; "her book" tells you the owner is female. Russian agreeing possessives do the reverse: the form follows the gender of the book, not the owner. So мой ("my") changes shape depending on whether the thing I own is masculine, feminine, neuter or plural — even though I, the speaker, am one fixed person.
- мой брат — "my brother" (брат is masculine → мой)
- моя́ сестра́ — "my sister" (сестра́ is feminine → моя́)
- моё окно́ — "my window" (окно́ is neuter → моё)
- мои́ друзья́ — "my friends" (друзья́ is plural → мои́)
Мой брат живёт в Москве́, а моя́ сестра́ — в Ки́еве.
My brother lives in Moscow, and my sister lives in Kyiv. (мой for masc. брат, моя́ for fem. сестра́)
Где моё пальто́? Мои́ перча́тки уже́ в карма́не.
Where's my coat? My gloves are already in my pocket. (моё for neuter пальто́, мои́ for plural перча́тки)
The four agreeing possessives in the nominative
There are two patterns to learn. мой and твой decline identically; наш and ваш decline identically. (Его́, её, их — his/her/their — do not belong here; they never change, and they live on their own page.)
| Owner | Masc. | Fem. | Neuter | Plural |
|---|---|---|---|---|
| я → my | мой | моя́ | моё | мои́ |
| ты → your (sg., informal) | твой | твоя́ | твоё | твои́ |
| мы → our | наш | на́ша | на́ше | на́ши |
| вы → your (pl./formal) | ваш | ва́ша | ва́ше | ва́ши |
Notice the stress difference: мой/твой stress the ending (моя́, моё, мои́), while наш/ваш keep the stress on the stem (на́ша, на́ше, на́ши). The masculine forms мой, твой, наш, ваш are single-syllable and take no stress mark.
Э́то наш дом, а вон та́м — ва́ша маши́на?
This is our house, and over there — is that your car? (наш for masc. дом, ва́ша for fem. маши́на)
Твои́ де́ти таки́е воспи́танные!
Your kids are so well-behaved! (твои́ for plural де́ти)
Full declension
Because these are adjective-like, they take adjective-style endings through all six cases. The masculine and neuter share most forms (differing only in the nominative/accusative); the feminine has its own set; the plural is unified across genders. Here is мой in full — твой declines the same way (just swap мо- → тво-).
| Case | Masc. | Neuter | Fem. | Plural |
|---|---|---|---|---|
| Nom. | мой | моё | моя́ | мои́ |
| Gen. | моего́ | моего́ | мое́й | мои́х |
| Dat. | моему́ | моему́ | мое́й | мои́м |
| Acc. | = nom./gen.* | моё | мою́ | = nom./gen.* |
| Inst. | мои́м | мои́м | мое́й | мои́ми |
| Prep. | о моём | о моём | о мое́й | о мои́х |
* The masculine and plural accusative follow the animacy rule: for animate nouns the accusative copies the genitive (моего́ бра́та, мои́х друзе́й); for inanimate nouns it copies the nominative (мой дом, мои́ дома́). See the accusative animacy rule.
наш declines on the same adjective template, but with the soft-ish -е- vowel: наш / на́шего / на́шему / на́шим / о на́шем (masc.), на́ша / на́шей (fem.), на́ши / на́ших / на́шим / на́шими (pl.). ваш patterns identically (ваш, ва́шего, ва́шему…).
Я давно́ не ви́дел твоего́ бра́та.
I haven't seen your brother in a long time. (genitive твоего́ бра́та — animate accusative copies the genitive after не ви́дел)
Расскажи́ мне о свое́й но́вой рабо́те и о на́ших пла́нах.
Tell me about your new job and about our plans. (prepositional о на́ших пла́нах after о)
Why declining them is non-negotiable
When a possessive sits in front of a noun, it is part of the same case-marked noun phrase, so it must carry the same case. Saying в мой дом with an undeclined possessive is like saying "in I house" in English — the case marking falls apart. The possessive and the noun travel together: choose the case for the whole phrase, then both words take it.
Мы живём в на́шем но́вом до́ме уже́ год.
We've been living in our new house for a year now. (prepositional на́шем до́ме after в — both possessive and noun in the prepositional)
How this differs from English
English collapses the entire system into invariant words (my, your, our). Russian asks two questions English never forces you to ask: (1) What gender/number is the possessed noun? — which picks мой vs. моя́ vs. моё vs. мои́; and (2) What case is the whole phrase in? — which adds the declension ending. English has nothing like the second question for possessives at all. The upside is that once you can decline ordinary hard adjectives, the possessives мой/твой/наш/ваш cost almost no extra effort — they ride the same machinery.
The other big English-to-Russian shift is sorting out which possessive: English your is ambiguous (one person or many?), but Russian forces твой (one person you're on informal terms with) versus ваш (several people, or one person you address formally). Pick the wrong one and you've changed the social register, not just the grammar.
Common Mistakes
❌ Э́то мой сестра́.
Incorrect — сестра́ is feminine, so the possessive must agree: моя́, not the masculine мой.
✅ Э́то моя́ сестра́.
This is my sister. (моя́ agrees with feminine сестра́)
❌ Я живу́ в мой дом.
Incorrect — after в (location) the phrase is prepositional; the possessive must decline too: в моём до́ме.
✅ Я живу́ в моём до́ме.
I live in my house. (prepositional моём до́ме)
❌ Я не зна́ю твой брат.
Incorrect — брат is an animate direct object after не зна́ю, so the accusative copies the genitive: твоего́ бра́та.
✅ Я не зна́ю твоего́ бра́та.
I don't know your brother. (animate accusative = genitive твоего́ бра́та)
❌ Здра́вствуйте! Как ва́ши зову́т?
Incorrect — confusing ваш (your) with the verb; and the question is set: Как вас зову́т? Don't force a possessive where a personal pronoun belongs.
✅ Здра́вствуйте! Как вас зову́т?
Hello! What's your name? (the fixed phrase uses the pronoun вас, not a possessive)
Key Takeaways
- The agreeing possessives are мой, твой, наш, ваш — they decline like adjectives in gender, number and case.
- They agree with the possessed noun, not the owner: мой брат, моя́ сестра́, моё окно́, мои́ друзья́.
- мой and твой share one declension (моего́, мое́й, мои́м…); наш and ваш share another (на́шего, на́шей, на́шим…).
- Stress splits the two groups: мой/твой stress the ending (моя́, моё, мои́); наш/ваш keep stem stress (на́ша, на́ше, на́ши).
- Always decline the possessive together with its noun — choosing a case applies to the whole phrase (в моём до́ме, твоего́ бра́та).
- His/her/their (его́, её, их) and the reflexive свой are handled separately — они́ do not behave like мой.
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- His, Her, Their: его́, её, ихA1 — его́ (his/its), её (her) and их (their) are frozen genitive forms of он, она́, они́ — they never decline and never agree (его́ брат, его́ сестра́, его́ кни́ги, о его́ кни́ге). This page contrasts them with the agreeing мой/наш, warns about the его́ vs. него́ split, flags substandard *ихний, and shows how свой changes the meaning.
- Свой: The Reflexive PossessiveB1 — свой ('one's own') points back to the subject of the clause and agrees with the possessed noun like мой (свой/своя́/своё/свои́). It is what disambiguates Он лю́бит свою́ жену́ ('his own wife') from Он лю́бит его́ жену́ ('another man's wife'). This page gives the full declension, the subject-reference rule, why it can't stand in the subject slot, and the idiom свой челове́к.
- Personal Pronouns and Their DeclensionA1 — The full system of Russian personal pronouns — я, ты, он, она́, оно́, мы, вы, они́ — declined across all six cases (я → меня́, мне, мной, обо мне; они́ → их, им, и́ми, них). Covers the obligatory н- that third-person pronouns add after a preposition (его́ кни́га but у него́), the fact that он/она́/оно́ refer to grammatically gendered things (Где стол? — Он там), and why Russian — unlike Spanish or Italian — usually keeps its subject pronouns rather than dropping them.
- 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.
- Dative: FormsA2 — The dative (да́тельный паде́ж) answers кому? (to whom?). Singular: masc/neuter -у/-ю (столу́, музе́ю, окну́, мо́рю), feminine -а/-я → -е (кни́ге, неде́ле), feminine -ь → -и (но́чи), and the -ия/-ие → -ии exception (Росси́и, ле́кции). Plural is uniform across all genders: -ам/-ям (стола́м, кни́гам, моря́м, музе́ям). The pronoun datives are мне, тебе́, ему́/ей, нам, вам, им, себе́. The trap: the feminine dative singular looks identical to the prepositional (both кни́ге), so the FORM is shared but the FUNCTION differs.
- Prepositional: FormsA1 — The prepositional (предло́жный паде́ж) endings — the one case that NEVER appears without a preposition. Singular: mostly -е (в столе́, в кни́ге, в окне́), but -ия/-ие/-ий and feminine -ь nouns take -и (в Росси́и, в зда́нии, о ле́кции, о но́чи). Plural: -ах/-ях for everyone (на стола́х, в кни́гах). Pronouns add н- after a preposition: о нём, о ней, о них.