Learn Hardcore Icelandic: Sonurinn er ungur og dóttirin er líka ung. - The son is young and the daughter is also young.

The spelling change is mostly about how Icelandic attaches endings. You don’t say dóttirinn; that would be considered wrong in standard Icelandic.

What is the role of er in the sentence?

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 are (singular, informal)
hann / hún / það er – he / she / it is
við erum – we are
þið eruð – you are (plural)
þeir / þær / þau eru – they are

So:

Sonurinn er ungur = The son is young
Dóttirin er ung = The daughter is young

Why is the adjective ungur in one place and ung in the other? Don’t they both just mean “young”?

They both mean “young”, but in Icelandic adjectives change form to agree with the noun in:

gender (masculine / feminine / neuter)
number (singular / plural)
case (nominative, etc.)

Here:

sonurinn is masculine singular nominative
- → adjective: ungur (masculine singular nominative)
- Sonurinn er ungur.
dóttirin is feminine singular nominative
- → adjective: ung (feminine singular nominative)
- Dóttirin er ung.

So the base meaning is the same, but the form of the word “young” changes to match the noun.

Why are the adjectives after er and not in front of the nouns, like “the young son”?

Because in this sentence “young” is part of the predicate, not an adjective directly modifying a noun.

Sonurinn er ungur.
Literally: The son is young.
Structure: [Subject] [verb “to be”] [adjective]

If you want “the young son” as a noun phrase, Icelandic normally puts the adjective before the noun, with different endings:

ungi sonurinn = the young son
unga dóttirin = the young daughter

So:

After er (predicative): sonurinn er ungur
Before the noun (attributive): ungi sonurinn

Could I say “Sonurinn og dóttirin eru ung” instead of repeating er and ung?

You can certainly combine them into one clause, but the form of the adjective must match a mixed-gender plural subject.

Sonurinn og dóttirin eru ungir.
= The son and the daughter are young.

Explanation:

The subject “sonurinn og dóttirin” is plural and includes a masculine noun.
In Icelandic, a mixed group (masculine + feminine) uses the masculine plural adjective:
- masculine plural of ungur is ungir.

So:

Correct: Sonurinn og dóttirin eru ungir.
Incorrect: Sonurinn og dóttirin eru ung (wrong form).

The original sentence simply chooses to repeat the verb and adjective:

Sonurinn er ungur og dóttirin er líka ung.
The son is young and the daughter is also young.

When do I use er and when do I use eru?

Both are forms of vera (to be), but:

er = singular (is)
eru = plural (are)

Examples:

Sonurinn er ungur. – The son is young.
Dóttirin er ung. – The daughter is young.
Sonurinn og dóttirin eru ungir. – The son and the daughter are young.

So you use er for one subject, and eru for they / several things.

What exactly does líka mean here, and where does it go in the sentence?

líka means “also / too / as well.”

In this sentence:

Sonurinn er ungur og dóttirin er líka ung.
= The son is young, and the daughter is also young.

Typical placements for líka:

After the verb:
- Hann er líka þreyttur. – He is also tired.
After the subject (still usually early in the sentence):
- Hún líka er þreytt. – She also is tired. (more emphasis on she as the one who also is)

Here líka comes after “er”, which is very natural and common.

What does og do, and is the word order around it like English?

og means “and”.

The basic word order on both sides of og is usually Subject – Verb – Rest, very similar to English:

Sonurinn er ungur – The son is young
og – and
dóttirin er líka ung – the daughter is also young

So the structure is:

[Subject] [er] [adjective] og [Subject] [er] [líka] [adjective].

Word order in simple Icelandic main clauses is usually SVO, like in English.

How do you pronounce the words in this sentence approximately?

Very rough English-based approximations (not precise IPA, just to give a feel):

Sonurinn – roughly: SOH-nu-rin
- so as in so
- nu like new but very short, almost nuh
- final -rin like rin in rinse without the s
er – roughly: air but shorter
ungur – roughly: OONG-gur
- u like oo in book (but a bit different)
- ng as in sing
- ur like a short oor with a tapped r
og – roughly: somewhere between oh and og
- often pronounced like “og” with a very soft or almost lost g depending on dialect and speed
dóttirin – roughly: DOH-ttir-in
- dó like dough
- ttir: double t is pronounced sharply, and -ir is like ear but shorter and closer
- final -in like in in in
líka – roughly: LEE-ka
- lí like lee
- ka like kah

For accurate pronunciation, listening to native speakers or a TTS engine for Icelandic is essential.

What are the genders of sonurinn and dóttirin, and why does that matter?

sonur / sonurinn is masculine.
dóttir / dóttirin is feminine.

Gender matters because:

It affects the definite endings:
- masculine: -inn / -urinn → sonurinn
- feminine: -in → dóttirin
It affects adjective agreement:
- masculine: ungur → Sonurinn er ungur.
- feminine: ung → Dóttirin er ung.

So to form correct Icelandic, you must learn each noun’s grammatical gender and let adjectives and endings agree with it.