Learn Icelandic: Strákurinn kaupir stólinn. - The boy is buying the chair.

Because stólinn is the direct object receiving the action (being bought), so it must be in the accusative case. For masculine words like stóll that end in double -ll, they drop one l in the accusative, becoming stól. Then, we add the definite article -inn to get stólinn. If it were the subject doing the action, it would be stóllinn with two Ls!

Wait, so the definite ending for the accusative case is -inn, just like the nominative case?

Exactly! For most masculine nouns, the definite article suffix is -inn in both the nominative and accusative cases. The trick is that you attach it to the accusative version of the word. Since the accusative of stóll is stól, we just add -inn to the end of that.

Both strákurinn and stólinn end in -inn. How do we know which one is the subject?

We look at the base word before the ending. Strákurinn uses the full dictionary form (strákur + inn), so it is in the nominative case (the subject). Stólinn uses the accusative form (stól + inn), so it is the object. Plus, Icelandic usually uses the same Subject-Verb-Object word order as English.

Why doesn't the Icelandic sentence have a word for "is" (as in "is buying")?