Learn Icelandic: Það er mikið af eyðslu um helgina. - There is a lot of spending over the weekend.

The phrase mikið af (a lot of) requires the noun that follows it to be in the dative case. Eyðsla is a weak feminine noun, and those always change their ending from -a to -u in the dative case.

Since eyðsla is a feminine noun, why do we use the neuter word mikið instead of the feminine mikil?

When you use the phrase mikið af (a lot of) to talk about quantities of an uncountable noun, it acts as a fixed set phrase. The word mikið stays in the neuter singular form regardless of the gender of the noun that comes after af.

What case is helgina in the phrase um helgina?

It is in the accusative case. The preposition um (over or around) takes the accusative. The word helgi (weekend) is feminine, and adding the definite article "the" to it in the accusative case makes it helgina. This is the standard way to say "over the weekend" in Icelandic.

Why do we start the sentence with Það er?

Icelandic uses Það er exactly like the English phrase "There is" to introduce that something is happening or exists. It acts as a placeholder subject when the real focus of the sentence (mikið af eyðslu) comes later.