Learn Hardcore Icelandic: Gítarinn hennar er gamall en fallegur.

The ending -inn is the masculine singular nominative definite article. Other genders/cases use different endings, but the key idea is: noun + ending = “the” + noun.

Why is it gítarinn hennar and not hennar gítarinn, like “her guitar” in English?

In everyday Icelandic, possessive pronouns like hennar (her) usually come after the noun:

bíllinn hennar = her car
húsið hans = his house
gítarinn hennar = her guitar

You can put hennar before the noun (hennar gítar), but that sounds either old‑fashioned, very formal, or very emphatic, and it’s rare in normal speech. The neutral, default word order is:

[noun + definite article] + [possessor]
→ gítarinn hennar

What exactly is hennar? Does it change for gender or number?

Hennar is the genitive form of the pronoun hún (she), used as a possessive: her.

hún = she
hennar = her / hers

Important points:

Hennar itself does not change for the gender or number of the thing owned:
- gítarinn hennar = her guitar (masc.)
- bókin hennar = her book (fem.)
- húsið hennar = her house (neut.)
It always refers to a third‑person feminine owner (a “she”), not to “I”, “you”, etc. (those have other possessives: minn, þinn, hans, þeirra, etc.).

What gender is gítarinn, and why does that matter for gamall and fallegur?

Gítar is a masculine noun. In the sentence:

Gítarinn hennar er gamall en fallegur.

the subject gítarinn is masculine singular nominative, so the adjectives describing it must agree with it in:

gender: masculine
number: singular
case: nominative (subject case here)

So we use the masculine singular nominative forms:

gamall (old, masc. nom. sg.)
fallegur (beautiful, masc. nom. sg.)

If the noun were feminine or neuter, the adjective forms would change, e.g.:

bókin hennar er gömul = her book is old (fem.)
húsið hennar er gamalt = her house is old (neut.)

Why is it gamall and not something like gamal or gamli?

The basic dictionary form of the adjective is gamall (old). It is irregular and changes a lot in other cases/genders:

Masculine nominative singular (strong): gamall → used here after er
Feminine nominative singular: gömul
Neuter nominative singular: gamalt

When an adjective comes after a linking verb like er (is), you normally use the strong form that matches the noun. For a masculine singular subject (gítarinn), the correct strong form is gamall, not gamli.

Gamli is the weak form used when the adjective is directly in front of a definite noun:

gamli gítarinn hennar = her old guitar
(adjective directly modifies a definite noun → weak form)

Why do we say er gamall en fallegur and not repeat er, like er gamall en er fallegur?

In Icelandic, as in English, you normally don’t repeat the verb when two adjectives share the same verb:

English: The guitar is old but (is) beautiful.
Icelandic: Gítarinn hennar er gamall en fallegur.

Both gamall and fallegur are predicate adjectives linked to gítarinn hennar by the same er (is), so you say the verb only once.

You could repeat er for special emphasis (e.g. in careful or poetic style), but in normal speech and writing you do not.

What does en mean here, and what’s the difference between en and og?

Here en means “but”:

Gítarinn hennar er gamall en fallegur.
= Her guitar is old but beautiful.

Compare:

og = and
- Gítarinn hennar er gamall og fallegur.
  = Her guitar is old and beautiful (no contrast implied)
en = but (contrasts two qualities)
- gamall en fallegur = old but beautiful

So en adds a slight contrast: it’s old, yet still beautiful.

Why are the adjectives after the verb here? Could I instead say something like hennar fallegi gamli gítar?

In this sentence, the adjectives are predicative (they come after er and state something about the subject):

Gítarinn hennar er gamall en fallegur.
→ Her guitar is old but beautiful.

If you put adjectives before the noun, they become attributive and take (usually) weak forms when the noun is definite:

Gamli fallegi gítarinn hennar
= her old, beautiful guitar

So both structures are possible, but they mean slightly different things:

[Noun] er [adjective]
- Focus on stating properties as a comment:
  Her guitar is old but beautiful.
[Adjective + adjective + noun]
- Describes the noun as a unit:
  her old, beautiful guitar

Your suggested spelling would need the weak forms: fallegi, gamli, not fallegur, gamall, if you put them directly before a definite noun.

Why do gamall and fallegur look different? Are they just two random patterns?

They follow two different but regular patterns:

fallegur is a regular adjective of the -legur type:
- masc. nom. sg.: fallegur
- fem. nom. sg.: falleg
- neut. nom. sg.: fallegt
gamall is an irregular adjective:
- masc. nom. sg.: gamall
- fem. nom. sg.: gömul
- neut. nom. sg.: gamalt

So they both obey the same rule (adjectives agree with noun in gender/number/case), but gamall happens to have irregular stems and vowels.

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

The verb and word order would stay the same, but the adjectives would change to match the noun’s gender:

Masculine (as in your sentence):
- Gítarinn hennar er gamall en fallegur.
Feminine:
- Bókin hennar er gömul en falleg.
  (Her book is old but beautiful.)
Neuter:
- Húsið hennar er gamalt en fallegt.
  (Her house is old but beautiful.)

This shows clearly how the adjective endings change with gender.