Aðstandandinn hringir þegar næturþjónustan kemur eftir byltuna.

Aðstandandi usually means a relative, next of kin, or sometimes a close person connected to the patient/resident.

The ending -inn is the definite article attached to the noun, so:

• aðstandandi = a relative / a next of kin
• aðstandandinn = the relative / the next of kin

Icelandic usually adds the to the end of the noun instead of putting a separate word in front, unlike English.

Hringja is the infinitive, meaning to call / to phone.

In the sentence, the subject is singular: aðstandandinn. So the verb has to be in 3rd person singular present tense:

• aðstandandinn hringir = the relative calls / is calling

The same thing happens with kemur:

• koma = to come
• kemur = comes / is coming

Here þegar introduces a time clause and means when.

Depending on context, it can sometimes feel close to as soon as. So this sentence could be understood as:

• when the night service comes
• or, in some contexts, as soon as the night service comes

That slight difference usually depends on the situation, not on a different form of the word.

Næturþjónustan is a compound noun:

• nætur- = night-
• þjónusta = service

So næturþjónusta means something like night service, night-duty service, or night staff/service depending on context.

Then the definite article is added at the end:

• næturþjónusta = night service
• næturþjónustan = the night service

This is very common in Icelandic: compounds are made first, and then the article is attached to the whole word.

Yes. Icelandic often uses the present tense where English might also use present, or sometimes will.

So this sentence can describe:

• a habitual action: The relative calls whenever the night service comes after the fall
• a future situation: The relative will call when the night service comes after the fall

This is especially normal in time clauses with words like þegar.

The noun is bylta, meaning a fall.

Here it appears as byltuna, which is the form meaning the fall after the preposition eftir in this sentence.

So:

• bylta = a fall
• byltuna = the fall

And:

• eftir byltuna = after the fall

In other words, this is not about physically going behind something. It means after the incident of falling.

Because after þegar, Icelandic normally uses ordinary subordinate clause word order:

• þegar næturþjónustan kemur = when the night service comes

That means the subject comes before the verb here.

A useful comparison is this:

• Aðstandandinn hringir þegar næturþjónustan kemur.
• Þegar næturþjónustan kemur, hringir aðstandandinn.

In the second version, the þegar-clause comes first, so the main clause shows the typical Icelandic verb-second pattern: hringir aðstandandinn.

It can depend on context.

Literally, it means the night service, but in real usage it can refer to:

• the night-duty service
• the night shift staff
• the night nurse/carer team
• the night worker as a service role

So even though the word looks like it names a service, it may practically refer to the people on duty at night.

You would remove the definite endings:

• aðstandandi instead of aðstandandinn
• næturþjónusta instead of næturþjónustan
• byltu instead of byltuna

So the indefinite version would be:

Aðstandandi hringir þegar næturþjónusta kemur eftir byltu.

That would mean something like A relative calls when a night service comes after a fall.

In practice, though, the definite version often sounds more natural if the people and event are already known in the situation.

These two letters are very important in Icelandic:

• þ is like the th in thin
• ð is like the th in this (though its exact sound can vary a bit depending on position)

So in this sentence:

• þjónustan begins with þ, like thin
• aðstandandinn contains ð, like this

English speakers often confuse these at first, but Icelandic keeps them as two separate letters.