Questions & Answers about Þetta er eitt af stærstu meistaraverkunum.
Why is 'meistaraverkunum' in the dative case here?
The preposition af always takes the dative case. In the einn af (one of) construction, the group you are choosing from will always be in the dative plural.
Why does 'meistaraverkunum' have the definite article attached to it?
In Icelandic, the "one of..." construction requires the noun to be definite, exactly like English where we say "one of the masterpieces". So the dative plural meistaraverkum (masterpieces) gets the definite suffix to become meistaraverkunum (the masterpieces).
Why do we use the neuter form 'eitt' instead of 'einn'?
Why is the adjective 'stærstu' used here instead of 'stærstum'?
Stærstu is the weak form of the superlative adjective stærstur (biggest). Because the noun meistaraverkunum is definite, the adjective describing it must use the weak declension. For superlative adjectives in the plural, the weak ending is always -u for all cases and genders.