Russian indefinite pronouns: –то and –нибудь

In Russian, question words like who, what, where, when, how change their meaning the moment you attach -то or -нибудь to them. Suddenly they stop asking a question and start pointing at someone, something, some place or some time — just not exactly which one.

These are called indefinite pronouns, and the whole topic comes down to one question: does the speaker have something specific in mind, or not?

Question words (base forms)

First, the basic question words these forms are built from:

• кто — who
• что — what
• где — where
• когда́ — when
• как — how
• како́й — which / what kind of

On their own, these words are used in questions. Add –то or –нибудь, and they turn into something else entirely.

–то = something specific, but unknown to the listener

Use –то when:

• the speaker believes the thing or person exists
• it's specific — the speaker just doesn't know (or isn't saying) exactly what or who

Forms:

• кто́-то — someone
• что́-то — something
• где́-то — somewhere
• когда́-то — once / at some point (usually past)
• ка́к-то — somehow (in some particular way)
• како́й-то — some kind of (agrees like an adjective: кака́я-то, како́е-то, каки́е-то)

Sentences:

• Кто-то звони́т. — Someone is calling.
• Я что́-то слы́шу. — I hear something.
• Он где́-то ря́дом. — He is somewhere nearby.
• Я когда́-то жил в По́льше. — I once lived in Poland.
• Он ка́к-то стра́нно говори́т. — He speaks somehow strangely.
• У меня́ есть кака́я-то иде́я. — I have some idea (a specific one, I just haven't said it).

The speaker is sure the thing or person exists — they just don't (or won't) name it.

–нибудь = anyone / anything, no particular one in mind

Use –нибудь when:

• it doesn't matter which one
• you're talking about the future, a request, or a possibility
• you mean "any" or "ever" — often inside questions

Forms:

• кто́-нибудь — anyone
• что́-нибудь — anything
• где́-нибудь — anywhere
• когда́-нибудь — someday / ever
• ка́к-нибудь — somehow (any way at all)
• како́й-нибудь — any kind of (agrees like an adjective: кака́я-нибу́дь, како́е-нибу́дь, каки́е-нибу́дь)

Sentences:

• Есть кто́-нибудь до́ма? — Is anyone home?
• Купи́ что́-нибудь к ча́ю. — Buy something for tea.
• Мы встре́тимся когда́-нибудь. — We'll meet someday.
• Мы ка́к-нибудь реши́м э́ту пробле́му. — We'll solve this problem somehow.
• Дай мне каку́ю-нибудь кни́гу. — Give me any book.

Nothing specific is fixed yet — any option works.

Note on "any": –нибудь still expects one answer to fall out eventually — it means "any, but something specific will get picked." It's not the same as true free-choice "any," the "no matter which, doesn't matter to me" kind. For that stronger meaning, Russian uses уго́дно instead — and unlike –нибудь, –то, and –либо, it's written as a separate word, with no hyphen:

• Дай мне что́-нибудь. — Give me something (one item, your choice, but still just one thing).
• Я могу́ говори́ть о чём уго́дно. — I can talk about anything (no restriction at all — see the Bonus section below).

Уго́дно is a big enough topic to get its own article: Что угодно: how to choose between уго́дно and –нибудь →. Worth finishing this one first, though — that article is the second part.

Note on pronunciation: –то and –нибудь are read as part of the same word as the question word — so there's only one stress in the whole word, and it stays on the question word itself, never moves to the ending. Because –то is unstressed, it reduces in pronunciation the way any unstressed "о" does in Russian — so it always sounds like [-та], not [-то]. Кто-то sounds like [ктота], где-то like [гдета], что-то like [штота].

The quick test: –то vs –нибудь

Ask yourself: does this thing/person already exist in a specific way, or is it still open?

• If you could point at it (even without knowing details) → –то.
• If it's hypothetical, future, or "any one will do" → –нибу́дь.

A useful trick: questions and requests about the future almost always take –нибудь, because the future hasn't happened yet — there's nothing specific to point at.

• Он принёс что́-то вку́сное на вечери́нку. — He brought something tasty to the party (it already happened — a specific thing he actually brought).
• Принеси́ что́-нибудь вку́сное на вечери́нку. — Bring something tasty to the party (a request about the future — no specific item in mind yet).

Кто, что and како́й also change by case

Where, when, and how never change — but кто and что decline like ordinary pronouns, and како́й declines like an ordinary adjective (agreeing in gender, number, and case with the noun it describes). The –то / –нибудь ending doesn't move — it just stays glued to the end after the case ending.

Кто-то / кто-нибудь and что-то / что-нибудь by case:

Worth adding a note that кого?/чего?/кому?/чему?/кем?/чем?/о ком?/о чём? aren't just abstract "case questions" — they're literally the declined forms of кто and что themselves. Students memorize them as question labels for identifying case, but don't always realize кого is кто in the genitive/accusative, чему is что in the dative, and so on. When кто-то/кто-нибудь needs a case, it's this same declension — the question word and the case form are the same word.

These question words decline exactly the way they do everywhere else in the language. If the case forms are unfamiliar, here's the overview: Russian Cases: The Logic Behind the System.

Како́й-то / како́й-нибудь by case (adjective-style):

*Accusative depends on animate vs. inanimate, same as regular adjectives.

Now the same idea, in real sentences — with the case ending doing its job before –то / –нибу́дь:

• Спроси́ у кого́-нибудь. — Ask someone (genitive, after у).
• Он говори́л с ке́м-то. — He was talking with someone (instrumental).
• Дай э́то кому́-нибудь. — Give this to someone (dative).
• Я ду́маю о чём-то ва́жном. — I'm thinking about something important (prepositional).
• Она́ чита́ет какую-то интере́сную кни́гу. — She's reading some interesting book (accusative, feminine).
• Расскажи́ мне о како́м-нибудь фи́льме. — Tell me about some movie (prepositional, masculine).

Common mistakes

🚫 Купи́ что́-то к ча́ю. (when asking someone to buy anything, their choice)

✔️ Купи́ что́-нибу́дь к ча́ю. — It's a request about the future with no specific item in mind — that's –нибу́дь territory.

🚫 Я когда́-нибудь жил в По́льше. (talking about a real past event)

✔️ Я когда́-то жил в По́льше. — A real thing that already happened needs –то, not –нибу́дь.

🚫 Есть кто́-то до́ма? (asking a genuine yes/no question about who might be home)

✔️ Есть кто́-нибу́дь до́ма? — You don't know if anyone is there at all — that's –нибу́дь, not –то.

🚫 Я могу́ говори́ть о чём-нибудь. (claiming you can talk about any topic, no restriction)

✔️ Я могу́ говори́ть о чём уго́дно. — "Anything" here means no restriction at all — that's the job of уго́дно, not –нибудь. –Нибудь still expects one particular topic to eventually get picked, just not decided yet — it doesn't mean "no matter what."

Bonus: what about ко́е- and –либо?

Two more indefinite pieces are worth knowing, though they're used less often:

• ко́е- (ко́е-кто́, ко́е-что́, ко́е-где́) — "a certain," used when the speaker knows exactly who/what but chooses not to say. Ко́е-кто́ мне сказа́л... — A certain someone told me... (the speaker knows who, and might be hiding it on purpose).

One thing to notice: unlike –то and –нибудь, which lean on the question word for stress and stay unstressed themselves, ко́е- carries its own stress. That means ко́е-кто́ actually has two stresses — one on ко́е, one on кто́ — instead of the single stress you get in кто́-то or кто́-нибудь.

• –либо (кто́-либо, что́-либо) — mostly the same "existential, not decided yet" meaning as –нибудь, just more formal and bookish — you'll meet it in writing, contracts, or news, rarely in everyday speech. In very formal or legal register it can occasionally stretch toward "no matter which" too, closer to уго́дно — but for everyday "anything at all," reach for уго́дно.

You don't need these for daily conversation, but recognizing them will stop you from being surprised when you meet them while reading.

Practice makes this click. The –то / –нибудь choice feels abstract on paper, but it shows up constantly in real conversation — so the more Russian you hear, the more automatic it becomes. That's exactly what the exercises above are for :)

One more thing: Exercises 3–4 up there already mix in уго́дно alongside –то and –нибудь — so if you're ready to add that third piece properly, the sequel is waiting: Что угодно →