Learn Hardcore Icelandic: Hún er róleg í dag.

Hún = she
er = is (3rd person singular of vera = to be)
róleg = calm, quiet, relaxed (feminine form of the adjective rólegur)
í = in (here used in a time expression)
dag = day (the word dagur “day” in the accusative singular, without an article)

So literally: “She is calm in day”, but idiomatically: “She is calm today.”

Why is it róleg and not rólegur?

Icelandic adjectives agree with the noun (or pronoun) they describe in:

Gender (masculine / feminine / neuter)
Number (singular / plural)
Case (nominative / accusative / dative / genitive)

Here, the adjective róleg- is describing hún (she), which is:

Feminine
Singular
Nominative (subject of the sentence)

The weak nominative singular forms of rólegur are:

Masculine: rólegi
Feminine: rólega

But in a predicative position after vera (to be), Icelandic normally uses the strong adjective endings:

Masculine: rólegur
Feminine: róleg
Neuter: rólegt

So:

Hún er róleg. – She is calm. (feminine, strong form)
Hann er rólegur. – He is calm. (masculine)
Barnið er rólegt. – The child is calm. (neuter)

That’s why you see róleg, not rólegur: it’s agreeing with feminine hún and using the strong form.

What exactly does róleg mean here – calm, quiet, or something else?

Róleg(ur) covers several nuances, depending on context:

Calm, relaxed, not stressed:
- Hún er róleg í dag. – She is calm/relaxed today.
Quiet, not noisy or agitated:
- Krakkarnir eru óvenju rólegir. – The kids are unusually quiet/calm.

In this sentence, Hún er róleg í dag, it usually means:

She’s calm / relaxed today,
Possibly also quieter than usual, not nervous or upset.

It does not normally mean “boring” or “emotionless”; just not tense, excited, or noisy.

Is this saying she is always a calm person, or just that she is calm today?

The phrase í dag (today) makes it clearly temporary:

Hún er róleg. – She is calm.
- Could mean either a general characteristic (She’s a calm person) or her current state, depending on context.
Hún er róleg í dag. – She is calm today.
- Strongly suggests this is about today’s state, possibly in contrast to other days.

So the sentence is understood as: “Today, she’s calm (even if maybe she isn’t always).”

Why is it í dag and not something like á dag or with an article?

Í dag is a very common fixed expression for “today.”

í literally means “in”, but with time words it often means “on / during / this”:
- í dag – today
- í kvöld – this evening, tonight
- í vetur – this winter

You do not use the article here. So:

Correct:
- Hún er róleg í dag. – She is calm today.
Incorrect / unnatural for “today”:
- ✗ Hún er róleg á dag.
- ✗ Hún er róleg í deginum.

Í deginum could exist in some very specific, more literal contexts (“in the day” as opposed to “in the night”), but for “today” you must use í dag.

What case is dag in, and why isn’t it dagur?

The base form of day is:

dagur – day (nominative singular)

The full declension (indefinite) is:

Nominative: dagur
Accusative: dag
Dative: degi
Genitive: dags

In í dag, the noun is in the accusative singular (dag).

Preposition í can take accusative or dative depending on meaning:

Í + accusative: movement into, or often a specific time span
- í dag – today
Í + dative: location in something (no movement)
- í skóla (dat.) – in school

So we get í dag (not í dagur).

Can I change the word order to Í dag er hún róleg? Is that different in meaning?

Yes, that’s perfectly correct:

Hún er róleg í dag.
Í dag er hún róleg.

The meaning is basically the same (“She is calm today”), but the emphasis changes slightly:

Hún er róleg í dag.
- Neutral; light emphasis on róleg í dag together.
Í dag er hún róleg.
- Emphasizes today more, a bit like “Today, she’s calm.”, often implying contrast:
  - She might be different on other days.

Both are very natural; the second just foregrounds “today”.

How do I make this sentence negative?

You insert ekki (not) after the verb er:

Hún er ekki róleg í dag.
- She is not calm today.

General pattern:

[Subject] + er + ekki + [adjective] (+ time phrase)
- Hann er ekki þreyttur. – He is not tired.
- Þau eru ekki tilbúin enn. – They are not ready yet.

So here: Hún er ekki róleg í dag.

How do you pronounce Hún er róleg í dag?

A fairly close IPA transcription (careful speaker) would be:

[huːn ɛr ˈrouːlɛɣ iː daːɣ]

Approximate English-style guidance:

Hún → “hoon” with a long oo (like food), but lips rounded: hoo-n
er → like English air but short and clear: ehr
róleg → ROH-leg
- ró: long “roh” (as in row),
- leg: “leg” with a soft final g (often like a soft fricative, almost like clearing your throat very gently).
í → like a long ee in see: ee
dag → daag, with a long a (somewhere between father and dog, depending on your English), and the final g also soft or weakened.

In everyday speech, the final g/ɣ sounds in róleg and dag may be quite light or almost disappear.

How would I say “They are calm today” instead?

You need a plural subject pronoun and a plural adjective. Which pronoun you choose depends on the gender of “they”:

Group of women only:
- Þær eru rólegar í dag.
  - þær – they (feminine)
  - rólegar – feminine plural of rólegur
Group of men only:
- Þeir eru rólegir í dag.
  - þeir – they (masculine)
  - rólegir – masculine plural
Mixed or neuter group (e.g. kids, animals, things):
- Þau eru róleg í dag.
  - þau – they (neuter)
  - róleg – neuter plural

So you choose according to the natural gender of the group.

Could I use an adverb instead, like “She is calmly today”?

In Icelandic, you almost always use an adjective with vera (to be) to describe someone’s state:

Hún er róleg í dag. – She is calm today.

An adverb (like rólega) is used to describe how someone does an action, not their state of being:

Hún talar rólega. – She speaks calmly.
Hún keyrir rólega. – She drives calmly.

So:

Correct:
- Hún er róleg í dag. – She is calm today.
Not idiomatic:
- ✗ Hún er rólega í dag.

Use the adjective (róleg), not the adverb (rólega), with er.

Is there any situation where I would use sé instead of er in a similar sentence?

Er is the indicative form (stating a fact):

Hún er róleg í dag. – She is calm today.

Sé is the subjunctive form, used in contexts like:

Reported / indirect speech or uncertainty:
- Ég held að hún sé róleg í dag.
  - I think (that) she is calm today.
Conditionals, wishes, hypotheticals:
- Ef hún sé róleg í dag, verður dagurinn auðveldur. (very formal/literary; spoken Icelandic more often keeps *er here)*

For a direct statement of fact like your original sentence, you use er, not sé.

Is this sentence formal or informal? Could I say it in everyday conversation?

Hún er róleg í dag. is completely neutral:

Suitable for everyday conversation
Also fine in more formal contexts

It uses basic vocabulary and standard grammar. You can say this naturally to friends, family, colleagues, or in written Icelandic.