Breakdown of Safnarinn er fullur af áhugaverðum hugmyndum.
vera
to be
hugmyndin
the idea
af
of (in quantity expressions)
safnarinn
the collector
Questions & Answers about Safnarinn er fullur af áhugaverðum hugmyndum.
Why does the adjective áhugaverðum end in -um?
The preposition af forces the following words into the dative case. Since hugmyndum (ideas) is plural, the adjective describing it must be in the dative plural. As you are learning in this lesson, strong adjectives in the dative plural always take the -um ending, perfectly matching the noun regardless of its gender.
Does the -um ending on hugmyndum tell us the gender of the noun?
No, it doesn't. In Icelandic, the dative plural ending for nouns is almost always -um, whether the noun is masculine, feminine, or neuter. Here, the base word hugmynd happens to be feminine, but you cannot tell that just by looking at its dative plural form.
Why is the word for full written as fullur here?
Fullur describes safnarinn (the collector). Because safnarinn is a masculine noun acting as the subject of the sentence (the nominative case), the adjective must match it by taking the masculine nominative singular ending -ur.
Why do we use af here instead of another preposition for of?
In Icelandic, the set expression for full of is fullur af. While af often translates to off or from in other contexts, it is the required preposition to use with the adjective fullur to express what something is filled with. It also dictates that the words following it must be in the dative case.