Learn Hardcore Icelandic: Ábyrgðin er mikil. - The responsibility is great.

It’s the subject of the verb er (is), so it must be in the nominative case.
The base noun ábyrgð is a feminine noun in Icelandic.
We’re talking about one responsibility, so it’s singular.

So: “feminine singular nominative definite” is the full description of Ábyrgðin here.

What is er here? Which form of the verb vera is it?

er is the 3rd person singular present form of the verb vera (to be).

Present tense of vera:

ég er – I am
þú ert – you (sg.) are
hann / hún / það er – he / she / it is
við erum – we are
þið eruð – you (pl.) are
þeir / þær / þau eru – they are

In Ábyrgðin er mikil, ábyrgðin is 3rd person singular (it), so we use er = is.

Why is the adjective mikil and not mikið or mikill?

The adjective mikill (big, great, much) changes its form to agree with the noun in gender, number, and case.

Nominative singular strong forms:

Masculine: mikill
Feminine: mikil
Neuter: mikið

Since ábyrgðin is feminine singular nominative, the adjective must also be feminine singular nominative strong:

Ábyrgðin er mikil. – The responsibility is great.

If the noun were neuter, you’d use mikið; if masculine, mikill:

Verkið er mikið. – The work (neuter) is great / a lot.
Kostnaðurinn er mikill. – The cost (masc.) is great / high.

Why is the adjective in the so‑called “strong” form here even though the noun is definite?

Icelandic distinguishes strong and weak adjective declensions:

Attributive adjectives (directly in front of a definite noun) normally use the weak form:
- hin mikla ábyrgð – the great responsibility
  - mikla = weak feminine nominative singular
Predicative adjectives (after vera and similar verbs) usually use the strong form, even if the noun is definite:
- Ábyrgðin er mikil. – The responsibility is great.
  - mikil = strong feminine nominative singular

So the rule is about position/function of the adjective:

before a definite noun → weak
after to be → generally strong

Could the word order be different, like Mikil er ábyrgðin, and would that change the meaning?

Yes, you can say:

Mikil er ábyrgðin.

Grammatically it means the same: “The responsibility is great.”
But the word order changes the emphasis:

Ábyrgðin er mikil. – neutral / normal statement; basic S–V–C word order.
Mikil er ábyrgðin. – more emphatic or stylistic, often poetic or formal; the focus is placed on how great the responsibility is.

In everyday speech and writing, Ábyrgðin er mikil is by far more common.

How would I say “The responsibility is not great” or “The responsibility is very great”?

You just add ekki (not) or a degree word like mjög (very):

Ábyrgðin er ekki mikil.
– The responsibility is not great.
Ábyrgðin er mjög mikil.
– The responsibility is very great.

Word order with ekki after er is the normal pattern for simple negation:

er ekki = is not

How is Ábyrgðin er mikil pronounced?

A fairly careful IPA transcription:

Ábyrgðin er mikil → [ˈauːpɪrɡðɪn ɛr ˈmɪːcɪl]

Some practical tips:

Á = like ow in cow, but longer: [auː]
y = a short i sound, like in bit: [ɪ]
r = trilled or tapped r
ð = voiced th as in this
In mikil, the k before i is palatal, somewhat like the k in cute, not like in car.

Rough English-friendly approximation: “OW-birg-thin ehr MEE-kil”, with main stress on Á‑ and MI‑.

Does ábyrgð always mean “responsibility”, or can it also mean “liability” or “guarantee”?

ábyrgð has several related meanings, depending on context:

Responsibility / duty (moral or practical)
- Ég ber mikla ábyrgð. – I bear great responsibility.
Liability (legal / financial)
- Ábyrgð bankans – the bank’s liability
Guarantee / warranty
- Tveggja ára ábyrgð á tækinu. – Two‑year warranty on the device.

In Ábyrgðin er mikil, it most naturally reads as responsibility is great, but in the right context it could also be “the liability is great”.

How would this sentence change if the noun were masculine or neuter instead of feminine?

The structure stays the same, but both the noun’s definite ending and the adjective ending change.

Masculine example

kostnaður – cost, expense (masc.)
Kostnaðurinn er mikill. – The cost is great / high.

Here:

kostnaðurinn = masc. sg. nom. definite
mikill = masc. sg. nom. strong

Neuter example

verkefni – project, task (neuter)
Verkefnið er mikið. – The project is big / substantial.

Here:

verkefnið = neut. sg. nom. definite
mikið = neut. sg. nom. strong

So you always match the adjective to the gender/number/case of the subject noun.

Is there any difference in nuance between Ábyrgðin er mikil and Það er mikil ábyrgð?

Yes, there is a subtle difference:

Ábyrgðin er mikil.
– The responsibility is great.
Focuses on a specific, already known responsibility. “The responsibility (we’re talking about) is large.”
Það er mikil ábyrgð.
– Literally: It is much responsibility.
More like a general or introductory comment, often translated as:
– That’s a lot of responsibility. / It’s a big responsibility.

The second structure (Það er…) is common when reacting to new information:

Þú verður forstjóri? Það er mikil ábyrgð.
– You’re going to be CEO? That’s a lot of responsibility.