This is the 822nd most frequent Icelandic word.
fjölskyldu
"Fjölskyldu" means "family" in English.
In this sentence, "fjölskyldu" is used in the accusative case, referring to the direct object "family" in the phrase "with my family".
Ég eyddi helginni með fjölskyldu minni.
I spent the weekend with my family.
Here, "fjölskylda" is used in the nominative case to describe the subject functioning equivalently to a collective noun representing 'the family'.
Við borðum kvöldmat saman sem fjölskylda.
We eat dinner together as a family.
In this case, "fjölskyldunnar" is in the genitive case to show possession, referring to 'my family's' relationship to the action.