The preposition o can mean “about” or “for,” and it takes two different cases depending on the meaning of the verb. The good news: the split is logical.

1. “o” + locative (6th) = about a topic

When o means “about” (a subject you speak or think of), it takes the locative — the “o kom, o čem” form.

  • mluvit o — to talk about
  • bavit se o — to chat about
  • číst o — to read about
Mluvil o mně.
He talked about me. (6th case: o mně)
Bavili jsme se o práci.
We chatted about work.

2. “o” + accusative (4th) = interest, care, asking, leaning

When o points toward a target — something you want, care for, ask for or lean on — it takes the accusative, the “o koho, o co” form.

  • zajímat se o — to be interested in
  • starat se o — to take care of
  • požádat o — to ask for
  • bát se o — to fear for
  • opírat se o — to lean on / against
Zajímal se o mě.
He was interested in me. (4th case: o mě)
Stará se o děti.
She takes care of the children.

3. The minimal pair to memorise

zajímal se o mě  (o koho, co — 4. pád)
he was interested in me — accusative
mluvil o mně  (o kom, čem — 6. pád)
he talked about me — locative

Even the pronoun looks different: mě (accusative) vs mně (locative). That little extra n is your clue.

“na” plays the same game: Dívali se na tebe. (4th — a target you look at) vs To závisí na tobě. (6th — a state/condition). Motion or target → accusative; location or state → locative.

The takeaway: don’t learn the preposition alone — learn verb + preposition + case as one chunk. “About a topic” → locative; “toward / for / caring about a target” → accusative.

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