Ég svara fundarboðinu strax svo lengi sem ég er ekki á vakt.

Because fundarboð is a compound noun:

• fundar- = of a meeting (from fundur, meeting)
• boð = invitation, message, notice, or summons, depending on context

So fundarboð is something like meeting invitation / meeting notice / meeting request.

The ending -inu shows that it is definite: the meeting invitation rather than just a meeting invitation.

That ending shows two things at once:

1. dative singular
2. the definite article (the) attached to the noun

The pattern here is:

• fundarboð = a meeting invitation
• fundarboði = to a meeting invitation / a meeting invitation (dative)
• fundarboðinu = to the meeting invitation / the meeting invitation (dative definite)

Icelandic usually adds the as an ending on the noun instead of using a separate word.

Because the verb svara normally takes a dative object.

So Icelandic says:

• svara einhverju = answer something / reply to something

That is why you get:

• Ég svara fundarboðinu = I reply to the meeting invitation

This is one of those verb patterns that English speakers simply have to learn: the case is controlled by the verb.

Because Icelandic often expresses that idea through case instead of a preposition.

In English, you often say reply to the invitation.
In Icelandic, you can simply say:

• svara boðinu

The dative case on boðinu already shows the relationship that English expresses with to.

So svara fundarboðinu is perfectly normal and natural.

It is the present tense, first person singular:

• ég svara = I answer / I reply

Compare:

• ég svara = I answer
• þú svarar = you answer
• hann/hún/það svarar = he/she/it answers

A useful thing to notice is that the dictionary form is also svara (with að svara = to answer), so the infinitive and the ég form look the same apart from að.

Strax means right away, immediately, or straight away.

So:

• Ég svara fundarboðinu strax = I reply to the meeting invitation immediately

Its placement is natural here: the object comes first, then the adverb.

Icelandic word order with adverbs can be somewhat flexible, but this version sounds very normal.

Here svo lengi sem means as long as or so long as.

It introduces a condition:

• svo lengi sem ég er ekki á vakt = as long as I am not on duty

Even though it literally looks like so long as, you should learn it as a fixed expression meaning provided that / as long as.

Depending on context, svo lengi sem can sometimes sound more like a time-span idea, but in this sentence it clearly works as a condition.

Because svo lengi sem introduces a subordinate clause.

In Icelandic main clauses, the verb often follows V2 word order, meaning the finite verb tends to come early. But in subordinate clauses, the order is more straightforward:

• sem ég er ekki á vakt

That is:

• sem = as long as
• ég = I
• er = am
• ekki = not
• á vakt = on duty

So after sem, the clause keeps the normal subject + verb order.

Because in Icelandic, ekki usually follows the finite verb in a simple clause like this.

So you get:

• ég er ekki = I am not
• hann kemur ekki = he is not coming / he does not come

That is why the sentence says:

• ég er ekki á vakt = I am not on duty

For English speakers, this is worth noticing because English puts not after an auxiliary verb, while Icelandic placement follows its own syntax rules.

Á vakt is an expression meaning on duty, on shift, or working a shift.

• á = on
• vakt = watch, guard, shift, duty

So:

• ég er á vakt = I am on duty / I am working a shift
• ég er ekki á vakt = I am not on duty

This is a very common everyday phrase, especially when talking about work schedules, healthcare, emergency services, retail, and similar jobs.