This is the 334th most frequent Icelandic word.
verkefninu
"The project" or "the task" (definite form).
Here, 'verkefninu' is used in the dative definite form, indicating the object of the verb 'að vinna'.
Ég er byrjuð að vinna að verkefninu.
I have started working on the project.
In this sentence, 'verkefninu' is in the dative definite form, which correlates with the verb 'kláruðum'.
Við kláruðum verkefninu í gær.
We completed the project yesterday.
'Verkefninu' appears in the dative definite form in this question, demonstrating its role in the context of reflection on the project.