pět a více + Genitive Plural

To become confident with this pattern, you must understand its strict syntactic boundaries and how it affects verb agreement.

• Direct Cases Only: For simple numbers (like 5, 10, 20), this rule only applies when the numeral phrase is in the nominative, accusative, or vocative cases. In oblique cases (genitive, dative, locative, instrumental), the rule generally vanishes for numbers 5–99. Instead, the numeral and the noun decline together into whatever case the preposition or verb demands (e.g., o pěti hodinách, never *o pěti hodin). Note that numerals 5–19 and the tens (20, 30, etc.) simply take the ending -i in all oblique cases (e.g., pět → pěti, dvacet → dvaceti), though note that 9 and 10 change their stem vowels (devět → devíti or devěti, deset → desíti or deseti). Higher numerals like sto (hundred) and tisíc (thousand) do not take the simple -i ending but decline like the nouns město and stroj, though sto frequently remains uninflected when followed by a counted noun (e.g., se sto muži). Furthermore, for these higher numerals (100, 1000, million, etc.), the genitive plural rule does not completely vanish in oblique cases; you can optionally keep the noun in the genitive plural (e.g., s třemi tisíci diváky or s třemi tisíci diváků). For compound numbers ending in 1 (like 21), the traditional prescriptive rule requires both the numeral and the noun to decline in the singular (e.g., k dvaceti jednomu žákovi). However, in modern usage, the numeral jedna often remains frozen while the noun takes the plural of the required case (e.g., k dvaceti jedna žákům in the dative plural). For compound numbers ending in 2–4, the last digit declines according to its own rules (e.g., k dvaceti dvěma žákům).
• Forming the Genitive Plural: Common patterns include adding -ů for masculine nouns (mužů, hradů), dropping the final vowel for hard feminine and neuter nouns (žen, měst), and adding -í for soft declension feminine and neuter nouns (růží, moří). Note that if dropping the final vowel creates a difficult consonant cluster, an -e- is inserted (e.g., matka → matek, jablko → jablek). Highly irregular and extremely common forms you must know are lidí (from lidé, people), dětí (from děti, children), peněz (from peníze, money), and dní or dnů (from dny / dni, days). Another crucial exception is the word for 'years' (rok), which often changes to let (e.g., pět let, dvacet let), though roků is also grammatically correct and widely used.
• Adjectives: Any adjectives modifying the counted noun must also take the genitive plural (e.g., pět nových aut, pět dobrých mužů).
• Verb Agreement: When a 5+ numeral phrase is the subject, the verb shrinks to the neuter singular in the past tense, and defaults to the 3rd person singular in the present tense. You must say Pět mužů přišlo (Five men came), not *Pět mužů přišli, and Pět mužů je tady (Five men are here), never *Pět mužů jsou tady.
• Compound Numbers: For compound numbers ending in 1, 2, 3, or 4 (e.g., 21, 22), the grammar depends on the form you choose. The single-word inverted form (e.g., jednadvacet, dvaadvacet) always triggers the genitive plural and neuter singular verb agreement (e.g., Dvaadvacet žen přišlo.). For the multi-word form (e.g., dvacet jedna, dvacet dva), standard Czech requires standard agreement: the noun takes the nominative singular after 1 (dvacet jeden muž, dvacet jedna žena) and the nominative plural after 2–4 (dvacet dva muži, dvacet dvě ženy, třicet tři auta), with corresponding verb agreement. Note that in colloquial, non-standard Czech (Common Czech), you might hear the multi-word forms frozen with the genitive plural (e.g., dvacet dva žen, dvacet dva studentů), but this should be avoided in formal writing.
• Quantifiers, Zero, and Large Numbers: Indefinite quantifiers like kolik (how many) and mnoho (many) follow this exact same rule. The number zero (nula) also triggers the genitive plural (e.g., nula bodů = zero points). Furthermore, hundreds (sto), thousands (tisíc), millions (milion), and billions (miliarda) also trigger this genitive plural and neuter singular verb rule.

Be careful not to confuse this with the number 1, which acts like a standard adjective, or numbers 2–4, which take the standard nominative plural and govern a plural verb.