The verb koskea (koskee jotakin / johonkin)

In Finnish, some verbs change their meaning depending on the grammatical case they govern. A common example is the verb koskea.

Koskea + Partitive: To Concern or Apply To

Koskea paired with the partitive case means "to concern" or "to apply to".

This ban absolutely applies to all visitors.
Tämä kielto koskee ehdottomasti kaikkia vierailijoita.
The information board concerns only feeding, you know.
Opastauluhan koskee vain ruokintaa.

Koskea + Illative: To Physically Touch

Koskea paired with the illative case (which often ends in a lengthened vowel + -n) means "to physically touch".

Do not touch the pony at the petting zoo.
Älä koske poniin kotieläinpihalla.
I wouldn't touch that animal pen.
En koskisi tuohon karsinaan.

Spotting the Difference

Because the meaning depends entirely on the case ending, both usages can appear side-by-side without confusion. Notice how poniin is in the illative case (touch), while sitä is in the partitive case (applies to):

The visitor touched the pony, even though the ban applies to it!
Vierailija koski poniin, vaikka kielto koskee sitä!