Breakdown of Fiskurinn lifir í vatninu.
vatnið
the water
í
in / into / to (before the hour, in telling time) / per (in frequency expressions)
fiskurinn
the fish
lifa
to live, to be alive
Questions & Answers about Fiskurinn lifir í vatninu.
Why do we use lifir here instead of býr? Both mean "lives", right?
English uses "to live" for both residing in a place and being alive, but Icelandic splits this. You use að búa for residing in a house or city. You use að lifa for being alive or existing in a natural habitat, which is why it is used for the fish here.
Why is the word for water spelled vatninu instead of just vatn?
Icelandic attaches the word for "the" to the end of the noun. The base word is the neuter noun vatn. Because it means "the water" and is in the dative case here, it takes the neuter dative definite suffix -inu.
Why does the preposition í force vatninu into the dative case here?
The preposition í can take either the accusative or the dative case. It takes the accusative when there is movement towards a destination, like jumping into the water. It takes the dative when describing a stationary position, meaning the fish is already located in the water.
How do we know Fiskurinn is the subject of the sentence?
The subject of an Icelandic sentence is usually in the nominative case. Fiskur is a masculine noun in its base dictionary form (nominative), and the attached definite article -inn is also in the nominative case, making it clear that the fish is the one doing the living.