Er sætið laust núna?

Because Icelandic yes/no questions usually put the finite verb first.

So the statement would be:

• Sætið er laust núna. = The seat is free now.

To turn that into a yes/no question, Icelandic switches the order:

• Er sætið laust núna? = Is the seat free now?

This is similar to English is the seat free?

Er is the present tense form of vera, which means to be.

Here it is the third-person singular form, because sætið is a singular noun, and singular nouns take third-person singular verbs in Icelandic:

• sætið er = the seat is

Because sætið means the seat, while sæti means a seat / seat.

Icelandic usually does not use a separate word like English the. Instead, the definite article is often added to the end of the noun.

So:

• sæti = seat
• sætið = the seat

In this sentence, -ið is the definite ending.

Sæti is a neuter noun.

That matters because in Icelandic, adjectives must agree with the noun they describe in gender, number, and often case. Since sætið is neuter singular, the adjective also has to be in a neuter singular form.

That is why the sentence uses laust.

The basic adjective is laus, but adjectives change form to match the noun.

Here are the singular forms:

• laus = masculine
• laus = feminine
• laust = neuter

Since sætið is neuter singular, the correct form is laust:

• sætið er laust

Usually in this kind of sentence it means free, empty, available, or unoccupied.

So if someone asks Er sætið laust núna?, they usually want to know whether nobody is sitting there at the moment, and whether they can use it.

Núna means now or right now.

It is an adverb of time. In this sentence it appears at the end, which is very natural:

• Er sætið laust núna?

That final position is a very common, neutral place for time adverbs. You may sometimes see adverbs in other positions, but this version is simple and standard.

Yes, definitely.

There is a small difference in focus:

• Er sætið laust núna? = Is the seat free now?
  This refers to a specific seat already understood from context.

• Er þetta sæti laust? = Is this seat free?
  This is especially natural if you are pointing at the seat.

Both are common and correct.

A rough English-friendly approximation is:

• er SIGH-tith löyst NOO-na

A few helpful notes:

• æ in sætið is roughly like eye
• au in laust is roughly like öy / oy
• ð is a soft th sound, like in this
• ú is a long oo sound

So sætið is roughly SIGH-tith, and laust is roughly löyst.