Common Mistakes: ten versus který | Czech Grammar

Two little words sit very close together in a learner's mind and constantly get swapped: the demonstrative ten / ta / to (that, the) and the relative pronoun který / která / které (which, that, who). Both can be translated by English that, which is exactly why English speakers mix them up. But they do completely different jobs. Ten points — it picks out a noun inside a single noun phrase. Který links — it opens a relative clause and ties it to a noun. This page walks through the specific errors that follow from confusing the two, with corrected forms.

The core distinction

Ten is a pointer. It stands next to a noun and says "that one, the one I mean": ten muž (that man), ta kniha (that book), to auto (that car). It never starts a clause; it has no verb hanging off it.

Který is a connector. It comes after a comma and begins a whole new clause that describes the noun: muž, *který přišel (the man *who came), kniha, *kterou čtu (the book *that I'm reading). It always has a verb in its clause.

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If you can replace the English word with "the one" → use ten (a pointer). If you can replace it with "who / whom / which" and a verb follows → use který (a clause opener).

Ten muž je můj soused.

That man is my neighbour. (ten points to the man — no clause)

Muž, který bydlí vedle, je můj soused.

The man who lives next door is my neighbour. (který opens a clause)

Líbí se mi ta červená bunda.

I like that red jacket. (ta points)

Líbí se mi bunda, kterou máš na sobě.

I like the jacket you're wearing. (kterou opens a clause)

Mistake 1: using ten to open a relative clause

The most damaging error is reaching for ten when you need a relativizer. Ten cannot link clauses — it has no clause-connecting power at all. A descriptive clause must be introduced by který (with a comma).

❌ To je ten muž, ten přišel včera.

Incorrect — ten cannot open the clause; you need the relativizer který.

✅ To je ten muž, který přišel včera.

That's the man who came yesterday.

Notice the correct version keeps ten in its proper job — pointing to muž — and then uses který to launch the clause. The two words happily coexist: ten points, který links. This pairing (ten ... který) is so common it has its own name, the correlative; see The Correlative ten ... který.

Vyber si tu knihu, kterou chceš.

Pick the book that you want. (tu points, kterou links)

Mistake 2: forgetting the comma before který

A Czech relative clause is always fenced off by a comma before který. This is not optional style — it is a punctuation rule, and skipping it is treated as an error. (English, by contrast, often omits the comma in restrictive clauses, which is precisely the habit to unlearn.)

❌ Kniha kterou jsem koupil je výborná.

Incorrect — a comma is required before který: Kniha, kterou…

✅ Kniha, kterou jsem koupil, je výborná.

The book I bought is excellent.

Note the second comma too: the relative clause is closed on both sides when the main sentence continues afterwards.

Mistake 3: not inflecting který for its role in the clause

Because English that and which barely change form, learners often freeze který in the nominative even when its job inside the clause demands another case. Remember the two-part rule from the který paradigm page: gender and number come from the antecedent, but the case comes from the role inside the relative clause.

❌ Žena, která jsem potkal, byla velmi milá.

Incorrect — která is the object of potkal, so it must be the accusative kterou.

✅ Žena, kterou jsem potkal, byla velmi milá.

The woman I met was very nice.

Mistake 4: wrong case for an animate masculine accusative

When the antecedent is an animate masculine and který is the object of the clause, the accusative is kterého (it borrows the genitive form), not který. This mirrors the noun itself: vidím muže, vidím kterého.

❌ Kolega, který jsem doporučil, dostal tu práci.

Incorrect — animate masculine object needs the accusative kterého.

✅ Kolega, kterého jsem doporučil, dostal tu práci.

The colleague I recommended got the job.

Mistake 5: using ten instead of který after a comma

A subtler version of Mistake 1: the learner correctly senses that a new clause is starting, even adds the comma, but still inserts a demonstrative form (ten / toho / tomu) where the relativizer belongs.

❌ Dům, ten jsme koupili loni, potřebuje opravu.

Incorrect — after the comma you need the relativizer: Dům, který jsme koupili…

✅ Dům, který jsme koupili loni, potřebuje opravu.

The house we bought last year needs repairs.

Mistake 6: kdo for things, co for people

This is a related confusion worth flagging. When the antecedent is a noun, the default relativizer is který, agreeing in gender and number. Learners sometimes substitute the bare question words kdo (who) or co (what) for it. As a relative attached to a specific noun, kdo and co are wrong; use který. (Kdo and co function as relatives only without a noun antecedent — ten, kdo to udělal "the one who did it" — see kdo and co.)

❌ To je ten člověk, kdo mi pomohl.

Incorrect — with the noun člověk as antecedent, use který, not kdo.

✅ To je ten člověk, který mi pomohl.

That's the person who helped me.

❌ Auto, co jsem si koupil, je červené.

Incorrect — co for a specific noun is colloquial at best; the standard form is které.

✅ Auto, které jsem si koupil, je červené.

The car I bought is red.

(In casual speech, co as an all-purpose relativizer — to auto, co jsem koupil — is widely heard, but it is (informal) and avoided in writing; který is always safe.)

A note for English speakers

The whole tangle comes from English using that for two unrelated jobs. That book (pointing) and the book that I read (linking) feel like the same word to an English speaker, so the brain offers a single Czech word for both. Czech keeps them strictly separate: ten points and stays inside the noun phrase; který links and opens a clause behind a comma. Whenever you are about to write a Czech that, ask whether a verb is about to follow it. If a verb follows, you are linking — use který with its comma and its clause-driven case. If no verb follows and you are just pointing at the noun, use ten. For the choice among the relativizers themselves (který, jenž, co, ten, kdo), see Choosing a Relative Word; for the full demonstrative paradigm, see Declension of ten, ta, to.

Key Takeaways

Ten points within a noun phrase ("that one"); který links a relative clause ("who / which / that" + verb).
A relative clause is always introduced by který and always preceded by a comma.
Ten can never open a relative clause — but it often precedes the antecedent in the ten ... který correlative.
Který takes gender/number from the antecedent and case from its role inside the clause; animate masculine objects use kterého.
Do not use kdo or co as the relativizer for a specific noun — that is the job of který.

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