Learn Hardcore Icelandic: Hún er mjög ánægð með börnin sín.

Hún – base form hún: she (3rd person singular feminine pronoun, nominative).
er – base form vera: to be. er is the 3rd person singular present tense.
mjög – base form mjög: very (degree adverb).
ánægð – base form ánægður: pleased, satisfied, happy (with something).
ánægð is the feminine singular nominative form.
með – base form með: preposition, roughly with.
börnin – base form barn: child.
börn = children (plural), börnin = the children (definite plural, nominative/accusative).
sín – base form sinn: one’s own (reflexive possessive pronoun).
Here sín is neuter plural nominative/accusative, agreeing with börnin (children).

Why is it ánægð and not ánægður or ánægt?

The adjective must agree with the grammatical gender, number, and case of the noun (or pronoun) it describes.

Subject: Hún (she) is feminine, singular, nominative.
Base adjective: ánægður (m.), ánægð (f.), ánægt (n.).

Because the subject is feminine singular, the predicate adjective takes the feminine singular nominative form:

Hún er ánægð – She is pleased.
If it were a man: Hann er ánægður – He is pleased.
If it were neuter: Það er ánægt – It is pleased / satisfied.

So ánægð matches hún in gender and number.

Why do we use með after ánægð?

Some Icelandic adjectives are typically followed by a fixed preposition, which may not be the same one you’d expect from English.

ánægður / ánægð / ánægt með e-ð = pleased with something.

So the normal idiomatic pattern is:

ánægð með eitthvað – pleased with something
ánægð með börnin sín – pleased with her children.

Using a different preposition (like við or af) after ánægð would sound wrong or at least very odd here.

What case does með take here, and how does that affect börnin?

The preposition með can take accusative or dative, depending on the meaning.

With the sense used in ánægð með e-ð (pleased with something), með takes the accusative.

So börnin is in the accusative plural definite:

Base noun: barn (child, neuter).
Plural: börn (children).
Definite plural: börnin (the children).

For barn, the nominative and accusative plural definite are both börnin, so you don’t see a form change, but grammatically it is accusative here because of með.

Why is it börnin and not just börn?

Börn = children (indefinite).
Börnin = the children (definite).

In Icelandic, when you talk about “her children” as a specific, known group (her own kids), it is very natural to use the definite form of the noun together with the possessive:

börnin sín – literally the children (of) her-own → her children.
Compare: bíllinn minn – my car (literally the car my).

So börnin sín reflects both definiteness (the children) and possession (her own).

What is the role of sín, and why don’t we say hennar?

sín is the reflexive possessive pronoun (from sinn), meaning “one’s own”. It’s used when the possessor is the subject of the clause.

In this sentence:

Subject: Hún (she).
Possessed thing: börnin (children).
We want to say: her own children, i.e. the children of the subject hún.

So we use sín, agreeing with börnin:

börnin sín – her own children (children of the subject hún).

hennar also means her, but it is non‑reflexive and is normally used when the possessor is not the subject:

Hann er ánægður með börnin hennar.
He is pleased with her children (some woman’s children, not his).

In a sentence where she is both the subject and the possessor, sín is the normal and expected form.

Could the sentence mean “She is very pleased with another woman’s children”?

Not as it stands.

Hún er mjög ánægð með börnin sín.
This strongly implies: She is very pleased with *her own children.*

To talk about another woman’s children, you would normally use hennar:

Hún er mjög ánægð með börnin hennar.
She is very pleased with her (another woman’s) children.

Native speakers would understand börnin sín as referring back to the subject hún, i.e. her own kids, not someone else’s.

Why does sín come after börnin instead of before it?

In Icelandic, most possessive pronouns (including the reflexive sinn / sín / sitt) usually come after the noun:

bíllinn minn – my car
húsið hans – his house
börnin sín – her own children

So noun + possessive is the default word order.

Putting sín before the noun (sín börn) would sound unnatural or wrong in normal prose. With sinn / minn / þinn etc., you do occasionally see pre‑posed forms in poetry or fixed expressions, but for learners, you should treat post‑position as the rule.

Why is it börnin sín and not börnin sínar or sína?

Because sín has to agree in gender, number, and case with börnin.

börnin is neuter plural (accusative).
The reflexive possessive sinn declines like minn.
The neuter plural nominative/accusative form of sinn is sín.

Relevant forms:

Neuter plural nom/acc: sín
Feminine plural nom/acc: sínar
Masculine plural acc: sína

Since börnin is neuter plural, the correct agreeing form is:

börnin sín – ✔ correct
börnin sína – ✖ would match masculine/feminine plural, not neuter.
börnin sínar – ✖ would be feminine plural.

So börnin sín is the grammatically correct combination.

Can we drop mjög, and what difference does that make?

Yes, you can drop mjög without changing the grammar:

Hún er ánægð með börnin sín.
She is pleased with her children.

mjög is just an intensifier:

mjög ánægð – very pleased.

So removing mjög makes the statement a bit weaker in intensity, but it is still perfectly natural and correct.

Is there a difference between ánægð and other words like glöð?

Yes, there is a nuance:

ánægð (from ánægður) – pleased, satisfied, content (with something specific).
Often used when you’re happy about a result, behaviour, performance, etc.:
- Hún er ánægð með börnin sín. – She is pleased with her children (e.g. their behaviour, progress).
glöð (from gladur / glöð / glatt) – glad, cheerful, happy (emotionally).
More about your general mood or joy:
- Hún er glöð. – She is happy/cheerful.

You can be both:

Hún er mjög glöð og ánægð með börnin sín.
She is very happy and pleased with her children.

But ánægð með specifically highlights satisfaction with something.

How is the sentence pronounced, especially ö and ð?

A rough pronunciation (not strict IPA, just learner‑friendly) is:

Hún er mjög ánægð með börnin sín
≈ Hoon ehr myœg AOW-naygth meth BEUR-nin seen

Some key points:

ú in hún – like long “oo” in food: [uː].
mjög – mj like English my
- ög with a rounded vowel, something like French peu: [mjœːɣ].
á in ánægð – like ow in cow: [au].
æg – often pronounced a bit like eye with a soft g/ɣ sound.
ð (in ánægð, með) – a voiced “th” as in this, but often quite soft and may almost disappear at the end of words.
ö in börnin – a rounded vowel, between e and u, similar to French peu or German ö in schön.
Final -in in börnin – like in in pin, but shorter.

Listening to native audio and repeating the full sentence a few times will help fix these sounds in your ear.