Case Agreement of Number + Noun in Oblique Cases

This is the subtlest point in the whole Czech numeral system, and it is where confident learners make their most stubborn mistake. The famous rule — "after five and up, the noun goes into the genitive plural" (pět žen, deset korun) — is true, but it is only half the story. It applies only when the numeral phrase is in the nominative or accusative. The moment the phrase lands in any other case — after a preposition, as an indirect object, in the instrumental — the genitive plural disappears and the noun simply agrees in that case, just like an ordinary noun. Once this clicks, a large part of advanced Czech syntax falls into place.

The two regimes

Think of a numeral phrase like pět žen as having two completely different modes depending on its syntactic role:

1. Nominative / accusative — the numeral 5+ behaves like a quantity word and governs the noun: the noun goes to the genitive plural, and the numeral itself doesn't change. Pět žen = "five women" (women = gen. pl.).
2. Any oblique case (genitive, dative, locative, instrumental) — the numeral declines, and the noun agrees with it in that very case, in the normal plural. o pěti ženách = "about five women" (both locative plural).

The genitive-plural government in mode 1 is not a property of the noun's meaning; it is a syntactic side effect of the numeral sitting in the nominative or accusative. Remove that condition and the side effect vanishes.

Read those two sentences side by side. Same five women, same noun, but ženách in the second one is not a genitive plural — it is the locative plural, agreeing with the locative numeral pěti.

The numeral itself declines

In oblique cases the numeral pět is no longer the bare quotation form — it takes endings of its own. The 5–10 numerals (and most higher ones) decline on a simple two-form pattern: a base form for nominative/accusative, and -i for every oblique case.

The genitive row deserves a careful look. pěti žen is genitive of the whole phrase (e.g. bez pěti žen "without five women"): here pěti is the genitive of the numeral and žen is genitive plural — but in this case both happen to be genitive, so it looks like the "old" rule even though it is really agreement. The dative, locative, and instrumental rows are where the contrast becomes unmistakable, because the noun takes a clearly non-genitive ending.

The vivid contrast

The brief asks for the switch to be made vivid, so here is the same noun, muž "man," in the nominative versus an oblique case.

That last one is the classic trap: s pěti muži, not s pěti mužů. "With five men" is instrumental throughout — the preposition s governs the instrumental, and that case spreads to both the numeral and the noun.

Why oblique cases override the genitive rule

The underlying logic is about who is in charge. A preposition (or a case-assigning verb) is "stronger" than a numeral: it imposes its case on the entire phrase it governs. When o demands the locative, the whole pěti ženách unit must be locative — the numeral cannot keep the noun in the genitive, because the numeral itself has been forced into the locative. The genitive-plural government only survives in the nominative and accusative because there is no stronger case-assigner present to overrule it. So the rule is not really an exception; it is a hierarchy: an external case-assigner beats numeral government every time.

The 2–4 numerals in oblique cases

Numerals 2, 3, 4 never govern the genitive — even in the nominative they agree (dva muži, tři ženy, čtyři města, all nominative plural). So in oblique cases they behave exactly as you'd expect: everything agrees, and there is no genitive surprise to unlearn.

Note the special instrumental/dative form dvěma — dva and oba "both" use dvěma for both the dative and the instrumental. The genitive plural of mužů in dvou mužů is again pure agreement (genitive throughout), not the 5+ government rule.

The practical upshot: in oblique cases, the 2–4 numerals and the 5+ numerals converge — both just agree with the noun. The famous split between "2–4 agree" and "5+ governs the genitive" only exists in the nominative and accusative. For the nominative-side behavior, see zero to four and five-plus and the genitive; for the full numeral paradigms, see declension of numerals.

Common mistakes

The dominant error is "genitive everywhere" — keeping the genitive plural the learner first memorized, even after a preposition.

Key takeaways

• The genitive-plural-after-5 rule fires only when the phrase is nominative or accusative: pět žen, pět mužů.
• In any oblique case (after a preposition, as an indirect object, in the instrumental), the numeral declines (pět → pěti) and the noun agrees in that case: o pěti ženách, s pěti muži, k pěti ženám.
• "With five men" is s pěti muži (instrumental throughout), never s pěti mužů.
• A preposition or case-assigning verb outranks numeral government — that is the whole rule.
• Numerals 2–4 already agree everywhere, so in oblique cases they behave just like the 5+ numerals.