Breakdown of Hvað langar þig að gera í kvöld?
hvað
what
gera
to do / to make (something) + adjective
langa
to want
að
to (infinitive marker)
Questions & Answers about Hvað langar þig að gera í kvöld?
Why do we use þig here instead of the normal word for you, þú?
The verb langa (to want) is special and uses a quirky subject. This means the person who wants something isn't in the normal subject form. Instead, they must be in the accusative case, so þú becomes þig.
If the sentence is about what "you" want, why doesn't the verb change to match "you"?
Because þig is a quirky subject, it doesn't control the verb like a normal subject does. The verb is frozen in the "he/she/it" form (third-person singular). It stays as langar no matter who is doing the wanting.
What is the purpose of the word að in this sentence?
The word að is the infinitive marker, just like the word "to" in English. It goes right before the dictionary form of a verb, so að gera simply means "to do".
How does í kvöld translate to "tonight"?
Literally, í kvöld means "in evening". Icelandic frequently uses the preposition í followed by a time of day to talk about "this" specific time, making í kvöld the standard way to say "tonight" or "this evening".