Questions & Answers about Uudet yhdistykset ovat tehneet hyvää työtä.
Why is the verb form tehneet instead of tehnyt?
Because the subject, yhdistykset (associations), is plural. In the perfect tense, plural subjects need the helping verb ovat and the plural past participle ending -neet. If it were just one association, it would be on tehnyt.
How do we get tehneet from the basic verb tehdä?
Tehdä (to do/make) is a type 2 verb. To make the past participle, you take the infinitive stem teh- by dropping the -dä, and then add the plural ending -neet.
The basic word for association is yhdistys. Where does the -kse- in yhdistykset come from?
Words ending in -us or -ys often change their ending to -ukse- or -ykse- before you add the plural -t or other case endings. So the stem of yhdistys becomes yhdistykse-, to which we add the plural -t.
Why are hyvää and työtä in the partitive case?
Because työ (work) is acting as an uncountable mass noun here. The associations have done an undefined amount of 'good work', so both the adjective and the noun take the partitive ending.