Learn Hardcore Icelandic: Við förum í ferðalag á frídögum.

So við förum literally means we go. You cannot say við fara; the verb must agree with the subject in person and number, so with við you need förum.

Does förum here mean we are going right now, or that we usually go (habitually)?

In Icelandic, the simple present tense (förum) is used both for:

actions happening now:
- Við förum núna – We’re going now.
habitual or repeated actions:
- Við förum í ferðalag á frídögum – We go on trips on days off.

In this sentence, the phrase á frídögum (“on days off / on holidays”) clearly signals a habitual meaning, so the sentence means we usually go on trips on our days off, not “we are going right now”.

What does the preposition í mean here, and why is it used with ferðalag?

Í most often corresponds to English in or into, but with travel and activities it is often used like English on:

í ferðalag – on a trip / on a journey
í frí – on vacation
í bíó – to the cinema

With motion verbs like fara (“go”), í often describes entering a place or state. Here you are going into the state of being on a trip, so Icelandic uses í ferðalag, literally “(go) into trip-ness”.

What exactly is ferðalag, and how is it different from ferð?

Both relate to travel, but there is a nuance:

ferð – a (single) trip, journey, ride, etc.
- Við förum í ferð – We go on a trip.
ferðalag – (usually) a trip/journey as an activity or process, often a bit more general or “journey-ish”.

In many everyday contexts, í ferð and í ferðalag can overlap and both can be understood as “go on a trip”. Ferðalag is a neuter noun and is a compound:

ferð (trip) + -alag (a nominalizing suffix)

Here it’s simply being used to mean a trip / a journey.

What case is ferðalag in, and how does í affect that?

Ferðalag is in the accusative singular here.

Base form (nominative sg.): ferðalag
Accusative sg. of this neuter noun: also ferðalag (same form)

The preposition í can take either accusative or dative:

í
- accusative = motion into / to something
í
- dative = being in / inside something

Examples:

Ég fer í skóla – I go to school (motion → accusative)
Ég er í skóla – I am in school (location → dative)

In Við förum í ferðalag, there is motion into the activity of a trip, so í takes the accusative, and we get ferðalag (accusative singular).

Where is the word for “a” in í ferðalag? Why isn’t there an article?

Icelandic does not have an indefinite article like English a / an. So:

ferðalag can mean a trip, one trip, or just trip in general, depending on context.

If the meaning is indefinite (“a trip”), Icelandic simply uses the bare noun:

í ferðalag – on a trip
kaupa bók – (to) buy a book

Definiteness (“the trip”) is usually shown by a suffix on the noun, not by a separate word:

ferðalagið – the trip
bókin – the book

So í ferðalag here corresponds to English “on a trip”.

What does á mean here, and why is it different from í?

Á is a very common preposition that most often means on, onto, or at. In time expressions like this, á + dative is used much like English on + day(s):

á mánudögum – on Mondays
á kvöldin – in the evenings
á frídögum – on days off / on holidays

So in this sentence:

í ferðalag – (go) on a trip (literally “into a trip”)
á frídögum – on days off

Here í governs the noun for the activity (the trip), and á governs the time expression.

What is the base form of frídögum, and what case and number is it in?

The base form is frídagur, a masculine noun meaning day off / holiday.

Its main forms:

Nominative sg.: frídagur – a day off
Accusative sg.: frídag
Dative sg.: frídegi
Nominative pl.: frídagar – days off
Accusative pl.: frídaga
Dative pl.: frídögum – on/for days off
Genitive pl.: frídaga

In á frídögum, the noun is in the dative plural, because the preposition á uses the dative in this type of habitual time expression (“on X days”).

Why is the plural frídögum used instead of a singular form like á frídegi?

Using the plural with time expressions is the normal way to talk about repeated/habitual actions:

á mánudögum – on Mondays (regularly)
á kvöldin – in the evenings (habitually; note that’s a special pattern)
á frídögum – on (our) days off / on holidays (whenever they come)

So á frídögum suggests “whenever we have days off, we go on trips”, not just on one specific day.

If you said á frídegi, that would sound like “on a (particular) day off”, a one-time event, and that doesn’t fit well with the habitual meaning of the sentence.

Can the word order change, for example to Á frídögum förum við í ferðalag?

Yes. Icelandic is quite flexible with fronting elements for emphasis, but the finite verb stays in second position (a typical Germanic “verb-second” rule).

Your two variants are both correct:

Við förum í ferðalag á frídögum.
- Neutral: We go on trips on days off.
Á frídögum förum við í ferðalag.
- Emphasis on the time: On days off, we go on trips.

In both cases, the finite verb (förum) is in second position:

[Við] förum …
[Á frídögum] förum við …

How is the whole sentence pronounced, especially ð, ö, and final -g in ferðalag and frídögum?

Approximate pronunciation (one common standard):

Við – [vɪːð]
- ð is a soft th sound, like in English this.
förum – [ˈfœːrʏm]
- ö is like the eu in French peur, or German ö in schön.
í – [iː] (long ee sound)
ferðalag – roughly [ˈfɛrðalaɣ]
- ð again like soft th in this.
- Final -g is often a soft, fricative sound [ɣ], not a hard “g”.
á – [auː] (like ow in cow, but longer)
frídögum – roughly [ˈfriːˌdœːɣʏm]
- The í is a long ee sound, [iː].
- ö again as in förum.
- -g- before ð / g can be quite soft; the final -g tends toward [ɣ].

Stress is on the first syllable of each word:
VIÐ förum Í FER-ða-lag Á FRÍ-dö-gum.