Learn Hardcore Icelandic: Í skóginum finn ég ró eftir langan dag í vinnu. - In the forest I find calm after a long day at work.

Case (dative)
The preposition í (“in”) normally takes the dative case when it expresses location (being in a place, not movement into a place).
- dative singular of skógur is skógi.
Definite article (“the”)
Icelandic usually attaches the word for “the” as an ending on the noun, not as a separate word.
- skógi (in a forest)
- skóginum (in the forest)

So the form is:

skógur (nom. sg., “forest”)
skógi (dat. sg., “forest”)
skóginum (dat. sg. + definite, “the forest”)

Could you also say Í skógi instead of Í skóginum? What’s the difference?

Yes, Í skógi is also grammatically correct. The difference is mostly about definiteness and how specific you’re being:

Í skógi
- literally “in a forest / in forest”
- more general or indefinite: in some forest, in the woods in general
Í skóginum
- literally “in the forest”
- more specific, or talking about “the woods” as a more concrete place you have in mind

In practice, both can often be translated as “in the forest / in the woods” in English, and the choice depends on how specific you feel the place is.

Why is the verb before ég in finn ég? Can’t it be Ég finn?

Both word orders are possible, but they have different structure and emphasis.

Icelandic main clauses are typically verb‑second (V2), like German:

The finite verb (here: finn) usually appears as the second element in the sentence.
One “chunk” can be placed in front of the verb for emphasis or as the topic.

In your sentence:

Í skóginum = first element (a prepositional phrase)
finn = second element, the finite verb
ég = subject, comes after the verb

So:

Í skóginum finn ég ró …
→ Literally: In the forest find I peace …
→ Emphasis on the location: it’s specifically in the forest that you find peace.

You can also say:

Ég finn ró í skóginum eftir langan dag í vinnu.

This is perfectly correct as well and sounds slightly more neutral, with less special emphasis on the place.

What case is ró in here, and why doesn’t it change form?

In this sentence, ró (“peace, calm, rest”) is the direct object of finn (“I find”). Direct objects in Icelandic are often in the accusative case.

For this noun:

nominative singular: ró
accusative singular: ró

So nominative and accusative look the same in the singular, which is why you don’t see any change.

There is also no article here because the meaning is indefinite:

Ég finn ró ≈ “I find peace / I find calm.”
Ég finn róna / róina would not be correct; the definite form is róin (“the peace”), so you’d say:
- Ég finn róina = “I find the peace” (very specific, and sounds odd in most contexts).

Abstract nouns like ró are very often used without the definite article when you just mean the general idea of “peace.”

Why is it eftir langan dag and not eftir langur dagur?

Because langan dag is in the accusative case, and the adjective and noun have to agree in case, gender, and number.

Noun: dagur (day) – masculine
- nominative sg.: dagur
- accusative sg.: dag
Adjective: langur (long) – strong masculine
- nominative sg. masc.: langur
- accusative sg. masc.: langan

In your phrase eftir langan dag:

eftir is a preposition meaning “after”
it is followed here by a time expression (“after a long day”)
that expression is in the accusative

So:

langur dagur = nominative, “a long day” as the subject of a sentence
- e.g. Langur dagur var það. – “That was a long day.”
eftir langan dag = accusative, “after a long day” as the object of the preposition eftir.

The change from langur dagur → langan dag is just normal case inflection.

What exactly does í vinnu mean, and how is it different from í vinnunni? Why not á vinnu?

Í vinnu is a very common phrase meaning something like:

“at work”
“working” (in the sense of being employed or on the job)

More precisely:

í vinnu
- literally: “in work”
- used for the state of being at work / having work
- e.g. Hann er í vinnu. – “He is at work / He is working (at his job).”
í vinnunni
- literally: “in the work” / “at the work”
- more concrete: “in the workplace,” “at that particular job”
- can also be used in the same sense as “at work,” but it feels a bit more specific or contextual:
  - Hann er í vinnunni núna. – “He’s at (his) work now.”

In your sentence, í vinnu focuses on “after a long day of working / at work” in a general sense.

Á vinnu is not idiomatic here. The preposition á is used with many locations (e.g. á skrifstofu “at the office”), but with vinna, the natural expression is í vinnu / í vinnunni, not á vinnu.

Which words are in nominative, accusative, and dative in this sentence?

Sentence: Í skóginum finn ég ró eftir langan dag í vinnu.

Nominative (subject):
- ég – “I”
Accusative:
- ró – “peace” (direct object of finn)
- langan dag – “(a) long day” (object of the preposition eftir in a time expression)
Dative:
- skóginum – “(the) forest” (object of í expressing location: in the forest)
- vinnu – “work” (object of í expressing state/location: at work)

Note about vinnu:
The noun vinna has the same form for accusative and dative singular (vinnu in both cases), but here, because í expresses a state/location (“at work”), it is understood as dative.

Are there other natural ways to say this same idea in Icelandic?

Yes, several variations are possible while keeping essentially the same meaning:

Changing word order (still natural):
- Ég finn ró í skóginum eftir langan dag í vinnu.
  (more neutral order: subject early, place later)
- Eftir langan dag í vinnu finn ég ró í skóginum.
  (emphasis on the “after a long day at work” part)
Slight vocabulary changes:
- Í skóginum næ ég ró eftir langan dag í vinnu.
  (ná ró = “to get/achieve peace”)
- Í skóginum finn ég hvíld eftir langan vinnudag.
  (hvíld = “rest”; vinnudagur = “workday”)

All of these would be understood in much the same way as the original sentence.