Learn Hardcore Icelandic: Nefið hans er oft kalt á veturna. - His nose is often cold in the winters.

Nefið hans is the normal, neutral order.
Hans nef is grammatical, but it sounds marked:
- more formal, written, or poetic, or
- with strong emphasis on his (as opposed to someone else’s):
  Hans nef er stærra en mitt. – HIS nose is bigger than mine.

For ordinary speech, Nefið hans is the standard phrasing.

What does the ending -ið in Nefið mean?

The ending -ið is the definite article (“the”), attached to a neuter singular noun:

nef – (a) nose
nef-ið – the nose

Icelandic usually adds the article as a suffix:

hús → húsið – the house (neuter)
stóll → stóllinn – the chair (masc.)
bók → bókin – the book (fem.)

So Nefið hans literally looks like “the nose his”, but it means “his nose”.

Could I say Nef hans er oft kalt á veturna without the -ið?

It’s grammatically possible, but it’s not the usual way to talk about someone’s body parts.

With body parts, Icelandic strongly prefers the definite form plus the possessive:

Höfuðið hans er stórt. – His head is big.
Augun hennar eru þreytt. – Her eyes are tired.
Nefið hans er oft kalt. – His nose is often cold.

Nef hans would sound less natural in this everyday sense.
The idiomatic choice here is Nefið hans.

Why is the adjective kalt and not kaldur?

Adjectives in Icelandic agree with the gender, number, and case of the noun.

Base forms of “cold”:

masculine: kaldur
feminine: köld
neuter: kalt

The noun nef (nose) is neuter. In the sentence:

nef-ið is neuter, singular, nominative, so
the predicate adjective must also be neuter, singular, nominative (strong) → kalt.

Compare:

Nefið hans er oft kalt. – His nose (neuter) is often cold.
Hundurinn hans er oft kaldur. – His dog (masc.) is often cold.
Hendin hennar er oft köld. – Her hand (fem.) is often cold.

What form is veturna in, and why is it used?

Veturna is accusative plural definite of vetur (winter).

Key forms:

singular: vetur (nom/acc), vetri (dat), vetrar (gen)
plural indefinite: vetur (nom/acc), vetrum (dat), vetra (gen)
plural definite: veturnir (nom), veturna (acc), vetrunum (dat), vetranna (gen)

In time expressions, Icelandic very often uses “á + accusative plural definite”:

á morgnana – in the mornings
á kvöldin – in the evenings
á sumrin – in the summers
á veturna – in the winters → in winter / during wintertime

So á veturna literally is “on the winters”, but idiomatically means “in winter (as a season in general)”.

Why does Icelandic use á here when English says “in winter”?

Prepositions don’t line up exactly between languages. In Icelandic, á is common where English uses in for time:

á morgnana – in the mornings
á sumrin – in the summers
á síðasta ári – in the last year
á veturna – in winter

So for the meaning “in winter (generally, every winter)”, the idiomatic phrase is á veturna, not í vetri or similar. It’s best to treat á veturna as a set expression you memorize.

Can I say á veturnum instead of á veturna?

Á veturnum uses the dative plural definite. It’s not wrong, but it tends to suggest particular winters or appear in slightly different contexts.

Very roughly:

á veturna (accusative plural definite):
usual, neutral way to talk about winter as a recurring season:
Nefið hans er oft kalt á veturna. – Every winter, his nose is often cold.
á veturnum (dative plural definite):
can be used if you mean some specific winters or in more marked styles.

For a general habitual statement like this one, stick with á veturna.

Where does the adverb oft usually go? Could I move it?

The neutral position for oft (often) is right after the finite verb:

Nefið hans er oft kalt á veturna.

Other positions are possible but change emphasis:

Oft er nefið hans kalt á veturna. – Emphasis on how often (OFTEN his nose is cold…).
Nefið hans er kalt oft á veturna. – Possible, but sounds less natural as a default.

As a learner, a safe rule: put frequency adverbs like oft after the verb.

How would you say “Their noses are often cold in winter”?

You need to make noun, verb, adjective, and possessive all plural:

nef → nefin – the noses (neuter plural definite)
hans → þeirra – their
er → eru – are
kalt → köld – cold (neuter plural)

The sentence:

Nefin þeirra eru oft köld á veturna.
Their noses are often cold in winter.

What is the difference between hans and sitt here? Could I say Nefið sitt er oft kalt á veturna?

Icelandic has:

Non‑reflexive possessives – hans, hennar, þeirra
Used when the possessor is not necessarily the subject of the same clause, or you just state ownership.
Reflexive possessive – sinn, sín, sitt (and its other cases)
Used when the possessor is the subject of the same clause and you mean “his own / her own / their own”.

Your sentence by itself:

Nefið hans er oft kalt á veturna.
Simply: His nose is often cold in winter. (The owner is some “he”.)

You can say:

Honum finnst nefið sitt oft kalt á veturna.
He feels that his own nose is often cold in winter.

Here sitt clearly refers back to honum / hann (him).
Without such a subject in the clause, Nefið sitt er oft kalt á veturna is odd on its own; Nefið hans… is the normal form.

How do you pronounce “Nefið hans er oft kalt á veturna”?

An approximate IPA transcription (standard Reykjavík pronunciation):

Nefið hans er oft kalt á veturna
[ˈnɛːvɪð hans ɛr ɔft kʰalt auː ˈvɛːtʏrna]

Piece by piece:

Nefið – [ˈnɛːvɪð] (long e, soft ð like th in this)
hans – [hans]
er – [ɛr]
oft – [ɔft] (short o like in off)
kalt – [kʰalt] (aspirated k)
á – [auː] (like English ow in cow)
veturna – [ˈvɛːtʏrna] (stress on ve‑, short rounded ʏ in the second syllable)

Stress in Icelandic is always on the first syllable of each word, so main word stresses are on NE‑fið, HANS, ER, OFT, KALT, Á, VE‑turna.