Breakdown of Strákurinn húkir hlæjandi í risinu, þar sem myrkrið er mest.
vera
to be
strákurinn
the boy
í
in / into / to (before the hour, in telling time) / per (in frequency expressions)
hlæja
to laugh
Questions & Answers about Strákurinn húkir hlæjandi í risinu, þar sem myrkrið er mest.
Why do we use þar sem for "where" in this sentence instead of hvar?
Hvar is strictly a question word used to ask "Where is something?". When you want to link two parts of a sentence to describe a location (meaning "in the place that"), you use the locative relative clause þar sem (which literally means "there as").
The English translation says "where it is darkest," but I don't see a superlative adjective like "myrkast". How does this work?
The Icelandic sentence actually uses a noun phrase here: myrkrið er mest literally translates to "the darkness is most" or "the darkness is greatest." Mest is the neuter superlative form of mikill (much/great). While you could say þar sem er myrkast (where it is darkest), using the noun with mest is a very common and natural way to express this in Icelandic.
Does the ending of hlæjandi (laughing) change depending on who is doing the laughing?
No! Hlæjandi is a present participle, functioning just like the English "-ing" form. In Icelandic, present participles always end in -andi and they never change their endings to match gender, number, or case.
Why is the attic (risinu) in the dative case here?