Learn Finnish: Tuo on harjoittelija, jonka taidot ovat hyvät. - That is an intern whose skills are good.

jonka is the genitive (possessive) form of the relative pronoun joka (who/which). Just like we say 'whose' in English to show possession, Finnish uses the genitive form jonka to show that the skills belong to the intern.

Why is the adjective hyvät in the plural form?

In Finnish, adjectives must match the number and case of the noun they describe. Since the noun taidot (skills) is in the nominative plural, the adjective hyvä (good) must also take the plural ending -t, becoming hyvät.

Does the word harjoittelija come from a verb?

Yes, it comes from the verb harjoitella (to practice). The -ja suffix is added to a verb stem to describe a person who does that action, similar to '-er' in English. So a person who practices or trains is a harjoittelija (intern or trainee).

Is the comma before jonka strictly necessary?

Yes, it is! In Finnish grammar, you must always use a comma to separate the main sentence from a relative clause (a phrase that starts with a relative pronoun like joka or jonka).