Numbers and Nouns Together

In Finnish, the relationship between a number and a noun changes depending on the grammatical case.

1. The Basic Rule (Nominative): As you learned with the number + partitive singular rule, numbers from 2 upwards govern the noun in the partitive singular (e.g., kolme kirjaa). The number zero (nolla) behaves exactly like numbers 2 and up.

2. The Agreement Rule (Oblique Cases): When the whole phrase is in a case like the genitive, inessive, or even the partitive (when required by negation or a verb), the number and the noun agree. This means:

• The number takes the case ending (e.g., kahden auton, kolmea autoa).
• The noun takes the same case ending.
• For regular countable nouns, the noun stays in the singular form, even though the meaning is plural (e.g., viidessä talossa).

3. Adjective Agreement: Adjectives follow the exact same rules as the noun, agreeing in case and number. In the basic nominative rule, the adjective also takes the partitive singular alongside the noun (e.g., kaksi isoa autoa, not kaksi isot autot). In oblique cases, they agree fully (e.g., kahdessa isossa autossa).

4. The Number One (yksi): The number yksi always agrees with its noun. In total object sentences, it takes the genitive-looking accusative (e.g., Ostin yhden kirjan), but in imperative or passive sentences, it takes the nominative-looking accusative (e.g., Osta yksi kirja!).

5. Teens (11–19): For numbers ending in -toista, only the first part of the number inflects. The suffix -toista remains unchanged. For example, kahdessatoista huoneessa (in twelve rooms).

6. Compound Numbers (20 and up): In compound numbers, every part of the number inflects. For example, 25 in the inessive case becomes kahdessakymmenessäviidessä huoneessa. However, in colloquial spoken Finnish (puhekieli), often only the final number is inflected (e.g., kakskytviidessä).

7. Millions and Billions: Words like miljoona (million) and miljardi (billion) behave like regular nouns and take the partitive singular themselves when counted. The noun that follows them also takes the partitive singular (e.g., kaksi miljoonaa euroa). In oblique cases, the number, the word miljoona/miljardi, and the noun all agree (e.g., kahdessa miljoonassa eurossa).

8. Plural Numbers (Collective Numerals): When a noun only exists in the plural (plurale tantum, like sakset or häät), the plural declension of the number must be used so it agrees with the plural noun. For example, kaksissa häissä (at two weddings).

9. Stem Changes and Consonant Gradation: Numbers often have special stems and undergo consonant gradation when a closed-syllable case ending is added. For example, the base stems kahte- (2) and viite- (5) weaken to kahde- and viide- (e.g., kahdessa, viidessä). Similarly, yksi becomes yhdessä.