Questions & Answers about Hún er dugleg og klárar verkefnið á réttum tíma.
Er is the present-tense, third-person singular form of að vera, which means to be.
So:
- ég er = I am
- þú ert = you are
- hann / hún / það er = he / she / it is
Since the subject is hún = she, er is the correct form.
Because dugleg is agreeing with hún, which is feminine singular.
The adjective duglegur changes form depending on gender:
- masculine: duglegur
- feminine: dugleg
- neuter: duglegt
Since the subject is feminine, Icelandic uses dugleg.
This is very common in Icelandic: adjectives often agree with the noun or pronoun they describe in gender, number, and sometimes case.