Learn Icelandic: Sérð þú fjögur jarðarber og þrjá sveppi? - Do you see four strawberries and three mushrooms?

In Icelandic, the numbers 1, 2, 3, and 4 change their form to match the gender and case of the noun they are counting! The verb sérð (see) makes the objects follow the accusative case. Because jarðarber (strawberries) is a neuter noun, we use the neuter accusative form fjögur. However, sveppi (mushrooms) is a masculine noun, so we use the masculine accusative form þrjá.

How do I know we need the accusative case here?

The verb sjá (to see) requires the thing you are seeing (the direct object) to be in the accusative case. Since you are seeing the strawberries and the mushrooms, both of those nouns—and the numbers attached to them—must be in their accusative forms.

Wait, why doesn't the word jarðarber (strawberries) have a plural ending?

Jarðarber is a neuter noun. In Icelandic, neuter nouns often look exactly the same in the plural as they do in the singular, at least in the nominative and accusative cases. So, one strawberry is eitt jarðarber, and four strawberries are fjögur jarðarber.

Why is the word for mushrooms sveppi here instead of sveppir?