Learn Hardcore Icelandic: Þeir eru að setja pakka undir ljósin. - They are putting a package under the lights.

Eru að setja is the Icelandic way to express the continuous or progressive aspect (“they are putting”). Icelandic lacks a dedicated progressive tense like English, so it uses the auxiliary vera in the present tense plus að + infinitive to show an action in progress. If you said just Þeir setja pakka undir ljósin, it could mean “they put packages under the lights” in a habitual or general sense, but it doesn’t clearly convey “right now.”

Why is setja in the infinitive form after eru að?

The word að is the Icelandic infinitive marker, equivalent to English “to.” Whenever you have vera + að, the main verb must be in its infinitive form. So setja stays as “to put” following að.

What case is pakka, and why does it look like that?

Pakka is the indefinite accusative form of the masculine noun pakki (“package”). Masculine nouns often take -a in the accusative singular, so pakki → pakka. Incidentally, the indefinite accusative plural is also pakka, so the form is ambiguous in number without context.

How can I tell if pakka refers to one package or several?

In the indefinite accusative, covers both singular and plural. You must rely on context or add numerals/adjectives. For one package you might say (nom.), but the object form is still ; for three packages you could say .