Breakdown of Hönnum plakatið fyrir viðburðinn!
fyrir
for (fyrir þig)
viðburðurinn
the event
hanna
to design
plakatið
the poster
Questions & Answers about Hönnum plakatið fyrir viðburðinn!
How does Hönnum mean "Let's design" here? Doesn't it just mean "we design"?
It's all about word order! While við hönnum means "we design", dropping the pronoun and putting the verb first (V1 word order) turns it into an exhortation. This is the most common way to say "Let's do something" in Icelandic.
Could we use við skulum for this sentence instead?
Yes, absolutely! The other common way to say "Let's..." is to use við skulum followed by the infinitive of the main verb. So you could say Við skulum hanna plakatið fyrir viðburðinn! and it would mean the exact same thing.
Why is viðburðinn in the accusative case here? Doesn't fyrir sometimes take the dative?
The preposition fyrir takes the accusative case when it means "for" in the sense of intended purpose or benefit (designing a poster for an event). It usually takes the dative when it refers to location (in front of) or time (ago). Because viðburður (event) is masculine, its accusative definite form becomes viðburðinn.
I see plakatið is the direct object, but it looks like the nominative dictionary form. Why didn't it change?
Plakat (poster) is a neuter noun. A handy rule in Icelandic is that all neuter nouns have the exact same form in both the nominative (subject) and accusative (direct object) cases. So the definite form is plakatið either way!