Fríið er búið, svo ég fer aftur í vinnu á morgun.

Fríið is frí + the definite article -ið.

• frí = vacation, holiday, break, time off
• -ið = the for a neuter singular noun

So fríið means the vacation / the break / the time off.

Because the noun already ends in -í, adding the article gives fríið.

Because búið agrees with fríið.

In this sentence, búið is part of the expression vera búinn / búin / búið, which means to be finished, done, over.

The form changes to match gender:

• búinn for masculine
• búin for feminine
• búið for neuter

Since frí is a neuter noun, Icelandic uses búið:

• Fríið er búið = The vacation is over

It is closely related, but the structure is a little different.

• Ég er búinn að borða = I have finished eating
• Fríið er búið = The vacation is over

With búinn að + infinitive, a person has finished doing something.

Here, there is no að + verb after it. The sentence is simply describing the state of the vacation: it is finished.

Here svo means so or therefore.

So the sentence is linking two ideas:

• Fríið er búið = the vacation is over
• svo ég fer aftur í vinnu á morgun = so I’m going back to work tomorrow

In other contexts, svo can also mean then or and then, so its exact meaning depends on context.

Because svo here is acting like a coordinating conjunction, and the clause keeps normal main-clause word order:

• svo ég fer...

So the order is:

• ég = subject
• fer = verb

A learner often expects inversion everywhere, but Icelandic does not automatically invert just because svo comes first.

Because Icelandic often uses the present tense for the near future when the time is already clear.

So:

• ég fer aftur í vinnu á morgun

naturally means:

• I’m going back to work tomorrow
• I’ll go back to work tomorrow

This is very normal Icelandic usage.

Fara í vinnu is a very common Icelandic expression meaning to go to work or to go back to work.

A few useful points:

• í here means into/to
• after movement, í often takes the accusative
• vinna is a feminine noun
• its accusative singular form is vinnu

So:

• í vinnu = to work / into work

In this sentence it feels general, like English back to work, so there is no article.

Yes, sometimes, but the nuance can be a bit different.

• í vinnu often sounds more general: to work, as an activity or state
• í vinnuna can sound more specific: to the job / to the workplace

In everyday speech, both can occur, but aftur í vinnu is a very natural way to say back to work.

Here it means back.

Icelandic aftur can mean both:

• again
• back

Context tells you which meaning is intended.

In this sentence, because the speaker was on vacation and is returning to work, back is the natural meaning:

• ég fer aftur í vinnu = I’m going back to work

This is a very common thing for learners to ask.

• á morgun = tomorrow
• í morgun = this morning

So in your sentence:

• á morgun = tomorrow

Even though it looks literally like on morning, you should learn á morgun as a fixed expression meaning tomorrow.

Not always. Frí is broader than just vacation.

Depending on context, it can mean:

• vacation
• holiday
• break
• day off
• time off

In this sentence, because the speaker says they are going back to work tomorrow, vacation or time off is the most natural interpretation.

Because Icelandic often leaves out possessive words like my when the meaning is obvious from context.

So:

• Fríið er búið

can naturally mean:

• The vacation is over
• My vacation is over

If the speaker is talking about their own situation, listeners will usually understand that it means my vacation without needing mitt or another possessive word.