In Icelandic, verbs dictate the grammatical case of their direct objects. While the vast majority of verbs take the accusative or dative case, a small, specific group of verbs requires their objects to be in the genitive case.
Many of these genitive-taking verbs are related to emotions, nostalgia, and experiencing things.
Missing and Remembering
Two very common verbs that govern the genitive case are sakna (to miss) and minnast (to remember, to recall). When you miss or remember something, that "something" must take the genitive form.
Notice how feminine nouns with the definite article, like fortíðin (the past) and sveitin (the countryside), change to fortíðarinnar and sveitarinnar in the genitive.
Enjoying and Expecting
When attending cultural events or indulging in experiences, you will frequently use the verbs njóta (to enjoy) and vænta (to expect). Both of these require the genitive case.
Whether you are expecting a specific outcome or a general concept, the object still takes the genitive case.
The Case Belongs to the Verb
It is important to remember that the genitive case is triggered strictly by these specific verbs, not by the nouns themselves. If you talk about the exact same topic using a different verb, the noun will change its case to match whatever that new verb requires.
For example, njóta takes the genitive (óperunnar), but útskýra (to explain) takes the accusative (óperuna).
Similarly, vænta takes the genitive (viðurkenningar), but fá (to get/receive) takes the accusative (viðurkenningu).