Declension of můj, tvůj, svůj | Czech Grammar

In English, my is a single frozen word: my brother, my sister, my car, my keys — the form never moves. Czech does not let you off that easily. The possessives můj (my), tvůj (your, singular), and svůj (one's own) are full pronouns that decline, and they agree in gender, number, and case with the noun they modify — that is, with the thing being possessed, never with the owner. The good news: all three share exactly the same endings. Learn the pattern of můj once and you automatically know tvůj and svůj.

Agreement is with the thing owned

This is the single idea that unlocks the whole topic. The possessor stays the same — I, me — but the form of my changes to match the gender of what is owned:

To je můj bratr.

That's my brother. (bratr is masculine → můj)

To je moje sestra.

That's my sister. (sestra is feminine → moje/má)

To je moje auto.

That's my car. (auto is neuter → moje/mé)

Same me, three different forms, because brother, sister, and car belong to three different genders. An English speaker's instinct is to keep můj fixed; resist it. The possessive behaves like an adjective glued to the noun, and it shifts with every gender, number, and case.

The full paradigm of můj

Czech offers two parallel sets of forms: contracted forms (má, mé, mí) and full forms in -oje / -oji / -ojí (moje, moji, mojí). They mean exactly the same thing. The contracted forms feel more formal and bookish; the full moje-forms dominate ordinary speech.

Singular	Masc. animate	Masc. inanimate	Feminine	Neuter
Nom.	můj	můj	má / moje	mé / moje
Gen.	mého	mého	mé / mojí	mého
Dat.	mému	mému	mé / mojí	mému
Acc.	mého	můj	mou / moji	mé / moje
Loc. (o…)	mém	mém	mé / mojí	mém
Instr.	mým	mým	mou / mojí	mým

Plural	Masc. animate	Masc. inanimate	Feminine	Neuter
Nom.	mí / moji	mé / moje	mé / moje	má / moje
Gen.	mých	mých	mých	mých
Dat.	mým	mým	mým	mým
Acc.	mé / moje	mé / moje	mé / moje	má / moje
Loc. (o…)	mých	mých	mých	mých
Instr.	mými	mými	mými	mými

tvůj and svůj run on identical rails: tvého, tvému, tvém, tvým; tvá/tvoje, tvé/tvojí, tvou/tvoji and svého, svému, svém, svým; svá/svoje, svou/svoji. If you can decline můj, you can decline all three without learning a single new ending.

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Watch the feminine spellings, because they trip up even good learners: accusative moji (with short -i) but genitive/dative/locative/instrumental mojí (with long -í). Vidím moji sestru vs bez mojí sestry.

můj running through the cases

Once you accept that the possessive moves with the noun, the cases follow naturally. Here is the same my threading through several cases and genders:

Vidíš mého bratra?

Can you see my brother? (masc. animate accusative)

Dej to mému bratrovi.

Give it to my brother. (masc. animate dative)

Bez tvého svolení to neudělám.

I won't do it without your permission. (neuter genitive)

Mluvil jsem se svou sestrou.

I was talking with my sister. (feminine instrumental)

O mé práci radši nemluvím.

I'd rather not talk about my job. (feminine locative)

Moji rodiče bydlí na vesnici.

My parents live in the village. (masc. animate nominative plural)

Notice that in se svou sestrou the form is svou, not mou. That is the reflexive possessive svůj doing its job: when the possessor is the subject of the clause, Czech strongly prefers svůj over můj/tvůj. It declines identically, but choosing between svůj and můj is a topic in its own right — see the overview of svůj.

Contracted vs full: which to use

In speech and informal writing, reach for the moje-forms by default — they are what you will hear all day in Prague:

Moje auto je zase v servisu.

My car is at the garage again. (everyday speech)

In formal, literary, or careful written Czech, the contracted forms are more elegant and expected:

Mé auto bohužel nebylo pojištěné.

My car was unfortunately not insured. (formal/written register)

Both are fully correct; neither is wrong. Mixing them in a single text is fine too — Czechs do it constantly. The plural mí rodiče (contracted) versus moji rodiče (full) is the same story: mí reads as slightly more formal, moji as everyday.

Common Mistakes

❌ Tohle je můj kniha.

Incorrect — kniha is feminine, so the possessive must be má/moje, not můj.

✅ Tohle je moje kniha.

This is my book.

❌ Znáš můj bratr?

Incorrect — a masculine animate direct object takes the accusative mého bratra.

✅ Znáš mého bratra?

Do you know my brother?

❌ Jdu s tvůj kamarád.

Incorrect — the preposition s takes the instrumental: tvým kamarádem.

✅ Jdu s tvým kamarádem.

I'm going with your friend.

❌ Neudělám to bez tvůj souhlas.

Incorrect — bez takes the genitive, so tvého souhlasu.

✅ Neudělám to bez tvého souhlasu.

I won't do it without your consent.

❌ Vrátil jsem můj klíč sousedovi.

Incorrect — the possessor is the subject, so standard Czech uses the reflexive svůj.

✅ Vrátil jsem svůj klíč sousedovi.

I returned my key to the neighbour.

Key Takeaways

můj, tvůj, svůj all decline with one shared set of endings — master můj and the other two are free.
The possessive agrees with the noun it modifies (the thing owned), not with the owner: můj dům, má kniha, mé auto.
Two interchangeable form-sets exist: contracted (má, mé, mí) for formal/written Czech, full (moje, moji, mojí) for everyday speech.
Mind the feminine spelling split: accusative moji (-i) vs the other oblique cases mojí (-í).
When the possessor is the subject of the clause, prefer the reflexive svůj over můj/tvůj.

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