Learn Icelandic: Hún notar oft tölvuna. - She often uses the computer.

Tölvan is the nominative form, which you use when "the computer" is the subject doing the action. Here, the computer is the direct object receiving the action (it is being used), so the verb nota forces it into the accusative case, becoming tölvuna.

How do we build the accusative definite form tölvuna?

First, take the base feminine noun tölva (computer) and change it to its accusative form, which is tölvu. Then, to say "the" computer, add the feminine accusative definite suffix -na. Together, tölvu + -na gives you tölvuna.

Why is the word order Hún notar oft... instead of Hún oft notar...?

In English, we say "She often uses", putting the adverb before the verb. Icelandic follows the V2 rule, meaning the main verb (notar) almost always insists on being the second element in the sentence. Since Hún takes the first spot, oft gets pushed to the third spot, right after the verb.

What is the infinitive (base form) of notar?

The base form is að nota (to use). Because the subject is hún (she), it takes the third-person singular present ending to become notar.