Learn Finnish: Kaksi toimikunnan jäsenistä äänestää huomenna. - Two of the committee members will vote tomorrow.

When you want to say "two of the members" (a specific subset of a known group), you use a number plus the elative case (-sta/-stä). If you used the partitive and said kaksi toimikunnan jäsentä, it would simply mean "two committee members" rather than highlighting them as a specific portion of the whole group.

Why is the verb äänestää in the singular when two people are voting?

In Finnish, when the grammatical subject of a sentence is a number other than one (here, kaksi), the verb must be conjugated in the third-person singular. Even though multiple people are acting, the grammar treats the number itself as a singular unit.

Why is toimikunta in the genitive case (toimikunnan)?

Toimikunnan is the genitive form of toimikunta (committee), expressing possession or belonging. It acts like an adjective here, translating directly to "the committee's". It must sit directly before the noun it modifies, which is why we get the chunk toimikunnan jäsenistä (of the committee's members).

How is the word jäsenistä built from its dictionary form?

The basic word is jäsen (member). Because we are talking about a group of members, we first need the plural stem, which is jäseni-. Then we attach the elative ending -stä (out of / from), resulting in jäsenistä.