Questions & Answers about Ég sé hesta en hann sér bílana.
Why is the word for horses hesta instead of hestar?
Because it is the direct object of the verb sé (see), so it must be in the accusative case. For most masculine nouns like hestur, the bare accusative plural ending is -a instead of the nominative (subject) plural ending -ar.
How do we get the form bílana for "the cars"?
The base word is bíll (car). Since it is the direct object of the verb, we need the accusative plural. The bare accusative plural is bíla (cars). To make it definite ("the cars"), we add the accusative plural definite suffix -na, giving us bílana.