The Adessive Plural (-illa/-illä)
The adessive case often expresses being on or at a location, but it is equally common for expressing the instrument or tool used to do something (like "with" or "by means of" in English).
To talk about using multiple tools, use the adessive plural ending -lla or -llä (depending on vowel harmony) attached to the plural stem, which includes the plural marker -i-. Any modifying adjectives must also take the adessive plural ending.
| I always clean with gloves. | Minä siivoan aina käsineillä. |
| We wash the table with white cloths. | Me pesemme pöydän valkoisilla liinoilla. |
| The cleaners clean the hospital with mops and machines. | Siivoojat siivoavat sairaalan mopeilla ja koneilla. |
Stem Changes
Adding the plural -i- often alters the final vowel of the word and can trigger consonant gradation:
- pesuaine (detergent) → pesuaineilla
- harava (rake) → haravoilla (final -a becomes -o-)
- luuta (broom) → luudilla (drops the final -a, and t softens to d)
| We clean the bathroom with good detergents. | Me siivoamme kylpyhuoneen hyvillä pesuaineilla. |
| The women cleaned the yard with brooms and rakes. | Naiset siivosivat pihan luudilla ja haravoilla. |
| Cleaners work with quiet vacuum cleaners. | Siivoojat työskentelevät hiljaisilla imureilla. |
| We always clean with the same tools. | Me siivoamme aina samoilla välineillä. |
Being "On" Plural Objects
While perfect for tools, the adessive plural also expresses being on top of plural items. A common example is tikkaat (ladder). Like "scissors" in English, tikkaat is a plural-only word in Finnish. To be "on the ladder," you must use the adessive plural.
| The father stands on the ladder. | Isä seisoo tikkailla. |
| Why do you sit on the ladder? | Miksi sinä istut tikkailla? |