Learn Finnish: Jokaisen vapaaehtoisen panos on tärkeä, vaikka keräys on pieni. - Every volunteer's contribution is important, even though the fundraiser is small.

It is in the genitive (possessive) case, showing ownership to mean 'every volunteer's'. When the pronoun jokainen takes a case ending, its basic -nen ending changes to -se- before adding the genitive -n marker.

Notice that both jokaisen and vapaaehtoisen end in -n. Is this a coincidence?

No, this is case agreement. In Finnish, pronouns and adjectives must match the case of the noun they modify. Because the noun vapaaehtoisen (volunteer's) is in the genitive case, the pronoun jokainen must also be in the genitive case (jokaisen).

If I wanted to say 'all volunteers' contribution', how would that differ from using jokaisen?

To say 'all volunteers', you would use the plural genitive form of kaikki (all), making it kaikkien vapaaehtoisten. Using jokaisen vapaaehtoisen (every volunteer's) keeps the grammar singular and places more emphasis on each person's individual effort.

Where does the word keräys (fundraiser) come from?

Keräys is a noun formed from the verb kerätä (to collect or gather). The -ys suffix is often added to verbs to create a noun that describes the action of doing that verb, much like '-tion' or '-ing' in English.