Flóamarkaðurinn er opinn í dag.

In Icelandic, the definite article is usually attached to the end of the noun rather than written as a separate word.

So:

• flóamarkaður = flea market
• flóamarkaðurinn = the flea market

This is very common in Icelandic. English says the market, but Icelandic often says the equivalent of market-the.

In this sentence, Flóamarkaðurinn is the subject, so it appears in the nominative singular definite form.

That ending comes from two things together:

• the noun’s nominative singular ending
• the attached definite article

The basic noun is:

• flóamarkaður = flea market

The definite form is:

• flóamarkaðurinn = the flea market

For many masculine nouns, the definite nominative singular looks like -urinn or something similar. So this is a normal masculine noun pattern, not something unique to this word.

Yes. Icelandic loves compound words.

flóamarkaður is made up of:

• fló = flea
• markaður = market

So it literally means flea market, just like in English.

A very useful thing to know about Icelandic is that long words are often just smaller words joined together.

Because opinn is an adjective, not a verb.

So the structure is:

• er = is
• opinn = open

Literally, the sentence works like:

• The flea market is open today.

This is similar to English: is + adjective.

Icelandic often uses vera (to be) with an adjective in exactly this way.

Because Icelandic adjectives have to agree with the noun they describe in gender, number, and case.

Here, Flóamarkaðurinn is:

• masculine
• singular
• nominative

So the adjective also has to be masculine singular nominative:

• opinn

Compare:

• markaðurinn er opinn = masculine singular
• búðin er opin = feminine singular
• húsið er opið = neuter singular

So opinn is chosen because flóamarkaður is a masculine noun.

í dag means today.

It is made of:

• í = in
• dag = day (an old case form used in this expression)

Historically, it is like saying in the day / on this day, but in modern Icelandic í dag simply functions as the normal expression for today.

It is written as two words because it is a preposition plus noun expression, not a single adverb.

Because Icelandic does not need one there.

English says today as a single word, and Icelandic uses í dag as a fixed expression. It does not normally mean in the day in the literal sense here, so no separate the is needed.

It is best learned as a set phrase:

• í dag = today
• á morgun = tomorrow
• í gær = yesterday

Yes. That is completely natural.

Icelandic word order is flexible, but the finite verb usually stays in the second position in main clauses. So both of these are good:

• Flóamarkaðurinn er opinn í dag.
• Í dag er flóamarkaðurinn opinn.

The difference is mainly emphasis:

• Flóamarkaðurinn er opinn í dag. = neutral statement
• Í dag er flóamarkaðurinn opinn. = extra focus on today

It means is open today, not opens today.

That is because:

• er = is
• opinn = open

So it describes the flea market’s state or condition today.

If you wanted to say opens today, you would need a different verb, such as one meaning open in the sense of begin operating.

A rough pronunciation guide is:

• Flóamarkaðurinn ≈ FLOH-a-mar-ka-thur-rin

A few helpful notes:

• ó is like o in go, but longer.
• ð is like the th in this.
• The stress in Icelandic usually falls on the first syllable, so FLÓA- gets the main stress.

You do not need perfect pronunciation right away, but it helps to notice that Icelandic almost always stresses the first syllable.

It is:

• Flóamarkaðurinn = subject
• er = verb
• opinn = predicate adjective
• í dag = time expression

So the pattern is:

• [subject] + [to be] + [adjective] + [time phrase]

That makes this a very useful model sentence. You can swap in other nouns, adjectives, and time expressions:

• Veitingastaðurinn er opinn í dag. = The restaurant is open today.
• Safnið er lokað í dag. = The museum is closed today.