The Locative of Topic with O | Czech Grammar

There is one construction you need before you can hold any real conversation in Czech: how to say what something is about. The answer is the preposition o plus the locative case. Talk about a film, a book about history, think about it — all of them use o + locative. This is the everyday Czech "about," and because the locative case appears almost exclusively after a preposition, o is one of the words that brings the case to life. The locative answers o kom? o čem? (about whom? about what?).

o + locative = the topic of speaking, thinking, knowing

Whenever a verb involves communicating or processing information — speaking, writing, reading, thinking, dreaming, knowing, hearing — the topic of that mental activity goes into o + locative:

Verb	Meaning	Example
mluvit o	to talk about	mluvíme o filmu
psát o	to write about	psát o cestování
číst o	to read about	číst o historii
přemýšlet o	to think about	přemýšlím o tom
vědět o	to know about	nic o tom nevím
snít o	to dream about	snít o cestě

Celý večer jsme mluvili o tobě.

We talked about you all evening. (ty → locative tobě)

Je to kniha o druhé světové válce.

It's a book about the Second World War. (válka → locative válce)

Vyprávěla mi o svém dětství.

She told me about her childhood. (dětství → locative dětství)

Nouns work the same way: a book, film, article or lecture about something takes o + locative — kniha o historii, film o válce, článek o klimatu.

Slyšel jsi o té nehodě na rohu?

Did you hear about the accident on the corner? (nehoda → locative nehodě)

The chunk o tom — "about it / about that"

If you learn one phrase from this page, make it o tom — about it / about that. It is one of the highest-frequency two-word combinations in spoken Czech, the natural way to refer back to something just mentioned. To (it/that) becomes tom in the locative.

Promiň, nechci o tom mluvit.

Sorry, I don't want to talk about it.

Nic o tom nevím.

I know nothing about it.

Pořád o tom přemýšlím.

I keep thinking about it.

The question form is just as common: o čem? (about what?) and o kom? (about whom?).

O čem to vlastně mluvíš?

What are you actually talking about?

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Bank o tom (about it), o čem? (about what?) and o kom? (about whom?) as ready-made chunks. They carry the locative ending for you, so you can use them correctly long before you've mastered the full ending system.

The endings on the noun

The noun after o takes its locative ending, which varies by gender and type. A few examples show the range (the full set of endings and their consonant changes lives on the locative endings page):

Type	Noun	o + locative	Note
Masc. animate	bratr	o bratrovi	-ovi for people
Masc. inanimate	film	o filmu	-u
Feminine -a	kniha	o knize	h → z softening
Feminine -a	Praha	o Praze	h → z softening
Neuter -o	město	o městě	-ě
Plural	děti	o dětech	-ech

Četl jsem zajímavý článek o Praze.

I read an interesting article about Prague. (Praha → locative Praze)

Pořád mluví jen o sobě.

He only ever talks about himself.

Don't confuse it with o + accusative

The preposition o is a two-case word. With the locative it means about (a topic). With the accusative it means for (after verbs of asking and striving) or by (a difference of degree). The verb usually tells you which:

o + locative (about a topic)	o + accusative (for / by)
mluvit o filmu — talk about a film	žádat o radu — ask for advice
kniha o válce — a book about the war	bát se o někoho — worry about someone
přemýšlet o tom — think about it	vyšší o hlavu — taller by a head

So mluvit o filmu (locative, the topic) but prosit o pomoc (accusative, what you're requesting). The accusative side of o is covered on the accusative prepositions page.

An honest exception: "ask about" is na, not o

There is one wrinkle worth stating plainly, because it breaks the neat pattern. Most cognition and communication verbs take o + locative for their topic — but ptát se ('to ask, to enquire') does not. To ask about someone or something, Czech uses na + accusative:

Volala mamka, ptala se na tebe.

Mum called, she asked about you. (ptát se na + accusative, not o)

Zeptej se v informacích na ten vlak.

Ask about that train at the information desk. (na + accusative)

There is no deeper logic to memorise here — mluvit o, přemýšlet o, číst o, but ptát se na. Learn ptát se na as a fixed exception and you've covered the one verb that doesn't follow the topic-o rule.

Common mistakes

❌ Mluvíme o film.

Incorrect — after o the noun must be in the locative (filmu), not the dictionary form.

✅ Mluvíme o filmu.

We're talking about the film. (o + locative filmu)

❌ Pořád na to přemýšlím.

Incorrect — 'think about' is přemýšlet o + locative, not na.

✅ Pořád o tom přemýšlím.

I keep thinking about it.

❌ Je to kniha na historii.

Incorrect — 'a book about X' is o + locative, never na.

✅ Je to kniha o historii.

It's a book about history.

❌ Ptal se o tebe.

Incorrect — 'ask about' is ptát se na + accusative, not o.

✅ Ptal se na tebe.

He asked about you.

❌ Nic o to nevím.

Incorrect — 'to' must take the locative 'tom' after o.

✅ Nic o tom nevím.

I know nothing about it.

Key takeaways

o + locative is the everyday way to express about — the topic of speaking, writing, reading, thinking, dreaming, knowing.
The chunk o tom (about it/that) and the questions o čem? / o kom? are extremely high-frequency; memorise them whole.
The noun takes a locative ending, often with a consonant change (kniha → o knize, Praha → o Praze).
Keep o + locative (topic) apart from o + accusative (asking for, difference by).
The one exception to learn: ptát se na
- accusative ("ask about"), not o.

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