Learn Hardcore Icelandic: Hún er oftast róleg í vinnunni, en fyrir próf er hún stundum stressuð. - She is usually calm at work, but before exams she is sometimes stressed.

In Icelandic, frequency adverbs like oft, oftast, stundum usually come right after the verb vera (er) and before the main describing word (adjective or participle).

So the neutral word order is:

Hún er oftast róleg í vinnunni.
Subject – er – frequency adverb – adjective – place

Hún er róleg oftast í vinnunni is grammatically possible, but it sounds marked and unnatural in everyday speech. It would sound like you are putting special emphasis on róleg, and oftast feels a bit “dislocated”. The standard, idiomatic choice is the original word order.

What is the difference between oft and oftast?

oft = often
oftast = most often / usually

Grammatically, oftast is the superlative form of oft:

oft (often) → oftar (more often) → oftast (most often)

So Hún er oft róleg means she is often calm, but Hún er oftast róleg means that most of the time / usually she is calm.

Why is the adjective róleg and not rólegur or rólegt?

Icelandic adjectives agree with the noun they describe in:

gender
number
case

The subject hún is feminine singular nominative, so the adjective also has to be feminine singular nominative:

masculine: rólegur
feminine: róleg
neuter: rólegt

Since hún is feminine, you must say Hún er róleg, not rólegur or rólegt.

Why is it í vinnunni and not just í vinnu or something with another preposition?

All three forms exist, but they have slightly different nuances:

í vinnunni
Literally in the work / in the job, with the definite article.
It often corresponds to at work (at her workplace), focusing on the place/situation.
í vinnu
Literally in work, indefinite.
Often means (to be) at work / working in a more general or activity sense, e.g.
Hún er í vinnu núna – She is at work (she is working now).
á vinnunni
This is also heard colloquially and can mean at work, but many speakers prefer í vinnunni in standard style.

In the sentence Hún er oftast róleg í vinnunni, the idea is “she is usually calm while she is at her workplace”, so í vinnunni is the natural choice.

What case is vinnunni, and why?

The noun vinna (work, job) here appears as vinnunni, which is:

feminine
singular
dative
definite

Form breakdown:

stem: vinna
dative singular: vinnu
definite dative singular: vinnunni

The preposition í takes:

accusative when it implies movement into something
dative when it implies location in something

Here it is location (in/at work), so í + dative → í vinnunni.

Why is it fyrir próf and not fyrir prófið?

Próf (exam/test) is a neuter noun where nominative and accusative singular and plural look the same: próf.

fyrir próf (no article) means before exams / before a test in a general, habitual sense – whenever exams come up, she is sometimes stressed.
fyrir prófið would mean before the (specific) exam, referring to one particular, known exam.

Since the sentence describes a typical pattern (not one specific exam), the indefinite fyrir próf is the natural choice.

What case is próf after fyrir, and why?

The preposition fyrir takes:

accusative with meanings like for, because of, before (time)

Here it means before (in time), so it governs the accusative case.

Próf in the accusative (both singular and plural) happens to be identical in form to the nominative: próf. So you do not see a visible ending change, but grammatically it is accusative after fyrir.

Why is stressuð used, and what form is it?

Stressuð is the feminine form of a past participle used adjectivally:

masculine: stressaður
feminine: stressuð
neuter: stressað

It comes from the verb að stressa (sig) – to stress (oneself), to be stressed.

Because the subject hún is feminine singular in the nominative, the participle must agree:

hún er stressuð – she is stressed

So stressuð is a feminine singular nominative form functioning as an adjective that describes hún.

Why does the sentence repeat hún in the second clause: en fyrir próf er hún stundum stressuð? Could it be left out?

In written Icelandic, you normally repeat the explicit subject hún in a new finite clause, even if it is the same person:

Hún er oftast róleg í vinnunni, en fyrir próf er hún stundum stressuð.

Dropping the subject (as in some “pro‑drop” languages) is not standard in Icelandic; you would not normally say:

✗ … en fyrir próf er stundum stressuð.

You need hún again to make the second clause complete and clear.

Is the word order en fyrir próf er hún stundum stressuð fixed, or can I say en hún er stundum stressuð fyrir próf?

Both are grammatical, but the emphasis and rhythm change slightly.

… en fyrir próf er hún stundum stressuð.
Fronting fyrir próf (before exams) highlights the time/situation; it sets the scene first:
“But as for the time before exams, then she is sometimes stressed.”
… en hún er stundum stressuð fyrir próf.
This keeps the more neutral order subject – verb – adverb – adjective – time phrase.
It sounds very natural and is probably the most typical spoken order.

So you can definitely say en hún er stundum stressuð fyrir próf; the original version just puts a bit more focus on the “before exams” part.

What does oftast … en stundum … imply about frequency compared to English?

oftast ≈ most of the time / usually
stundum ≈ sometimes

The contrast:

Hún er oftast róleg … en … stundum stressuð.

implies that her default state is calm, but there are exceptions (sometimes) when she is stressed, particularly before exams. This is very close to the English pattern “She is usually calm … but sometimes she is stressed …”

Why is the verb er used instead of something like er að vera to show “is being” stressed or calm?

Icelandic does not use a progressive form in the same way English does. The simple present er covers both English:

is (a state) and
is being (temporary state/behaviour)

So:

Hún er róleg can mean She is calm / She is being calm.
Hún er stressuð can mean She is stressed / She is being stressed.

You do not normally say er að vera róleg to mean is being calm; that sounds unnatural in Icelandic in this context.