This is the 46th most frequent Serbian word.
део
Part.
Here, 'део' means 'part', referring to a segment or piece of the collection.
Ово је важан део наше колекције.
This is an important part of our collection.
In this sentence, 'део' means 'part' and implies a portion of material covered in learning.
Научили смо само део градива до сада.
We have only learned a part of the material so far.
Here, 'део' refers to an assigned or expected segment of work.