Indefinite Pronouns: -то, -нибудь, кое- | Russian Grammar

Russian has no single word for "someone" or "something." Instead it builds an entire system of indefinite pronouns by attaching three particles — -то, -нибудь, and the prefix кое- — to the ordinary question words (кто, что, где, когда́, как, како́й, чей, ско́лько). The grammar is mechanical once you see it; the hard part — and the thing English never forces you to decide — is which particle to choose. The choice is not about politeness or style: it encodes whether the speaker has a specific, real referent in mind. Getting this right is one of the clearest markers of a fluent speaker.

The system at a glance

Take any question word and add the particle. The meaning shifts predictably:

Base	-то (specific, unknown)	-нибудь (any, non-specific)	кое- + (a certain one)
кто	кто́-то — someone	кто́-нибудь — anyone	ко́е-кто — a certain person
что	что́-то — something	что́-нибудь — anything	ко́е-что — a certain thing
где	где́-то — somewhere	где́-нибудь — anywhere	ко́е-где — here and there
когда́	когда́-то — once, at some time	когда́-нибудь — ever / sometime	—
како́й	како́й-то — some (kind of)	како́й-нибудь — any (kind of)	ко́е-како́й — a certain (kind of)

Note the stress: in the -то / -нибудь forms the stress stays on the question word (кто́-то, что́-нибудь), and the particle is unstressed. With кое-, the stress is on ко́е- (ко́е-кто, ко́е-что).

-то: specific but unknown to the speaker

-то says: the referent is real and definite — it exists — but I (the speaker) don't know who or what it is. Something did happen; someone did do it; I just can't identify them. Because it asserts a real event, -то lives naturally in the past and the present-as-fact.

Кто́-то звони́л, пока́ тебя́ не́ было.

Someone called while you were out. (a real, definite caller — I just don't know who)

Мне ка́жется, я где́-то ви́дел э́того челове́ка.

I feel like I've seen this person somewhere. (a real place exists in my memory; I can't pin it down)

Она́ что́-то шепну́ла ему́ на у́хо.

She whispered something in his ear. (a definite something was said)

The "specific but unknown" feel is the whole point: with -то there is a fact in the world that the speaker is gesturing at without being able to name.

-нибудь: non-specific, hypothetical, future

-нибудь says: any one will do — no particular referent is meant, perhaps none even exists yet. It is the particle of requests, questions, futures, conditions, and "whatever / anyone at all." The referent is open: when you say "call someone," you don't have a specific person in mind.

Позвони́ кому́-нибудь, кто разбира́ется в маши́нах.

Call someone who knows about cars. (anyone qualified — no specific person)

Хо́чешь что́-нибудь попи́ть?

Do you want something to drink? (offer — any drink at all)

Когда́-нибудь я обяза́тельно прие́ду в Япо́нию.

Someday I'll definitely come to Japan. (an open, future time — no fixed date)

Если кто́-нибудь спро́сит, скажи́, что я ско́ро верну́сь.

If anyone asks, say I'll be back soon. (hypothetical — there may be no asker at all)

💡

The rule of thumb that resolves most cases: -то for realis (something that actually happened or exists — typically past or present statements), and -нибудь for the irrealis zone — requests (imperatives), questions, the future, and conditionals. "Someone called" = звони́л кто́-то (it happened); "Call someone" = позвони́ кому́-нибудь (it hasn't yet, anyone will do).

The contrast in one minimal pair

Put the two side by side and the difference is sharp:

Он что́-то купи́л в магази́не.

He bought something at the shop. (a definite purchase happened — I just don't know what)

Купи́ что́-нибудь к ча́ю.

Buy something to go with the tea. (anything will do — the purchase hasn't happened yet)

Same question word, same case, opposite particles — and the meaning flips from "a real, mystery item" to "any item, your choice."

кое-: a certain one (I know, but won't say)

The prefix кое- is the mirror image of -то: here the speaker does know the referent but is choosing not to spell it out — "a certain person," "a certain something." It carries a hint of the confidential or the deliberately vague.

Мне ну́жно ко́е-что тебе́ сказа́ть.

I need to tell you a certain something. (I know exactly what — I'm just not naming it yet)

Ко́е-кто из на́ших друзе́й уже́ всё зна́ет.

A certain one of our friends already knows everything. (I know who; I'm being coy)

A small grammar note: with prepositions, кое- usually splits around the preposition in careful speech — ко́е с кем ("with a certain someone"), ко́е о чём ("about a certain something") — though the unsplit form is also heard colloquially.

The mechanics: attach the particle to the declined pronoun

This is the part learners get wrong structurally. The particle is invariable; it's the question word inside that declines, taking whatever case the verb or preposition demands. You decline кто/что first, then bolt on the particle:

nominative: кто́-то, что́-нибудь
genitive: кого́-то, чего́-нибудь
dative: кому́-то, кому́-нибудь
accusative: кого́-то (animate), что́-нибудь (inanim.)
instrumental: кем-то, чем-нибудь
prepositional: (о) ком-то, (о) чём-нибудь

Я ко́е с кем познако́мился на конфере́нции.

I met a certain someone at the conference. (instrumental кем inside ко́е, split by с)

Расскажи́ нам о чём-нибудь интере́сном.

Tell us about something interesting. (prepositional чём + -нибудь, after о)

With prepositions and -то/-нибудь, the preposition goes before the whole word: с кем-то ("with someone"), о чём-нибудь ("about anything") — the particle stays glued to the end of the declined pronoun.

How this differs from English

English uses "some-" for statements and "any-" for questions and negatives ("I saw someone" / "Did you see anyone?"), which is a rough analogue of the -то / -нибудь split — but only rough. English "any-" covers both Russian -нибудь (Хо́чешь что́-нибудь? "Want anything?") and Russian negatives (никто́, on the negative pronouns page), and English has nothing matching the "specific-but-unknown" nuance of -то or the "I-know-but-won't-say" nuance of кое-. The biggest transfer error is using -то in places where English "some-" feels natural but Russian needs -нибудь — namely imperatives, questions and futures. Train the reflex: is this a real, completed fact (-то) or an open/hypothetical case (-нибудь)?

Common Mistakes

❌ Позвони́ кому́-то, е́сли бу́дет ну́жно.

Incorrect — a request about an open, future referent needs -нибудь, not -то: кому́-нибудь.

✅ Позвони́ кому́-нибудь, е́сли бу́дет ну́жно.

Call someone if you need to. (-нибудь — request, no specific person)

❌ Ты что́-то хо́чешь пое́сть?

Usually wrong as a genuine offer — an open question/offer takes -нибудь: Ты что́-нибудь хо́чешь пое́сть?

✅ Ты что́-нибудь хо́чешь пое́сть?

Do you want something to eat? (-нибудь — open offer)

❌ Кто́-нибудь звони́л, пока́ тебя́ не́ было.

Incorrect as a report of a real event — a call that actually happened takes -то: Кто́-то звони́л.

✅ Кто́-то звони́л, пока́ тебя́ не́ было.

Someone called while you were out. (-то — a real caller)

❌ Я говори́л с кто́-то ва́жным.

Incorrect — the pronoun must decline before the particle; after с it's the instrumental кем: с кем-то.

✅ Я говори́л с кем-то ва́жным.

I spoke with someone important. (instrumental кем + -то after с)

❌ Я хочу́ ко́е-что-нибудь тебе́ сказа́ть.

Incorrect — кое- and -нибудь are mutually exclusive; use one. To mean 'a certain thing I'll tell you': ко́е-что.

✅ Я хочу́ ко́е-что тебе́ сказа́ть.

I want to tell you a certain thing. (кое- — I know what it is)

Key Takeaways

Indefinite pronouns = question word + particle: -то, -нибудь, or the prefix кое-.
-то = specific but unknown to the speaker; lives in the realis (past / present fact): Кто́-то звони́л.
-нибудь = non-specific / any; lives in the irrealis — requests, questions, futures, conditionals: Позвони́ кому́-нибудь.
кое- = "a certain one I know but won't name": ко́е-кто, ко́е-что (stress on ко́е-).
The particle is invariable; the question word inside declines to the case the verb/preposition needs: кого́-то, кому́-нибудь, с кем-то, о чём-нибудь.
Rule of thumb: -то for what really happened, -нибудь for what might.

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