Bensíntankurinn er næstum tómur, þannig að við verðum að stoppa.

Because Icelandic forms compound nouns very freely.

• bensín = petrol / gasoline
• tankur = tank

Together they make bensíntankur = gas tank / fuel tank.

Then the definite article is added to the end, giving bensíntankurinn = the gas tank.

This is very normal in Icelandic. Where English often uses separate words, Icelandic often prefers one compound word.

It is the definite article, meaning the.

So:

• bensíntankur = a gas tank
• bensíntankurinn = the gas tank

In Icelandic, the is usually attached to the noun instead of being a separate word. The exact form of the ending changes depending on the noun’s gender, case, and number, so you should think of -urinn as the form that fits this particular noun here, not as a universal ending for every word.

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

Here, bensíntankurinn is:

• masculine
• singular
• nominative

So the adjective must also be masculine singular nominative:

• tómur = empty

Compare:

• tankurinn er tómur = the tank is empty
• flaskan er tóm = the bottle is empty
• glasið er tómt = the glass is empty

This is a very common question. In Icelandic, an adjective used after a verb like er is usually in the strong/indefinite-looking form, even if the noun itself is definite.

So:

• bensíntankurinn er tómur = the gas tank is empty

But if the adjective comes before a definite noun, you normally get the weak/definite adjective form:

• tómi bensíntankurinn = the empty gas tank

So the difference is not just definiteness. It is also about position and function:

• predicate adjective after vera: tómur
• attributive adjective before a definite noun: tómi

Næstum means almost or nearly.

It modifies the adjective tómur, so næstum tómur means almost empty.

This word order is normal:

• næstum tómur = almost empty
• næstum búinn = almost finished
• næstum fullur = almost full

So here næstum is simply an adverb placed before the word it modifies.

Þannig að is a very common connector meaning something like:

• so
• so that
• therefore
• with the result that

In this sentence, it introduces the result of the first clause:

• the tank is almost empty,
• so we have to stop.

It is very common in everyday Icelandic.

No, they do different jobs.

1. In þannig að, að is part of a fixed expression/conjunction.

   • þannig að = so / so that

2. In verðum að stoppa, að is the infinitive marker.

   • að stoppa = to stop

So they look the same, but they are not functioning the same way.

Verðum is the 1st person plural present form of verða.

• ég verð
• þú verður
• hann/hún/það verður
• við verðum

On its own, verða often means become. But in the construction verða að + infinitive, it means:

• must
• have to

So:

• við verðum að stoppa = we must stop / we have to stop

This is an important expression to learn as a whole.

Because stoppa is an infinitive here, and Icelandic usually uses að before the infinitive in this kind of construction.

• að stoppa = to stop

So:

• við verðum að stoppa = we have to stop

This að works a lot like English to, although Icelandic does not use it in exactly all the same situations English does.

Yes. Stoppa is very common in everyday Icelandic.

It is the usual kind of verb you would hear in speech for stop, especially in contexts like travel, driving, or movement. In this sentence, it most naturally means something like stop the car / pull over / stop somewhere.

Even if the word originally came from outside Icelandic long ago, it is completely normal modern Icelandic.

A helpful quick guide is:

• þ is like the th in thin
• ð is like the th in this

So:

• þannig starts with the thin sound
• við contains the this sound

One extra detail: at the end of a word, ð can sound quite weak in natural speech, so við may not sound as strongly pronounced as an English learner expects.

Usually no. Icelandic normally keeps subject pronouns.

So:

• við verðum að stoppa = we have to stop

That is the normal, expected structure. Unlike languages such as Spanish or Italian, Icelandic does not usually drop subject pronouns just because the verb ending already shows the person.