Learn Hardcore Icelandic: Síminn hennar er bilaður.

Síminn = “the phone”; noun, masculine, nominative singular, definite (base form sími
- definite ending -inn).
hennar = “her”; independent possessive pronoun in the genitive; placed after the noun.
er = “is”; 3rd person singular present of vera “to be”.
bilaður = “broken/out of order”; adjective used for machines, serving as a predicative complement agreeing with the subject.

Why is the possessive after the noun (síminn hennar) instead of before it?

That’s the neutral Icelandic pattern for possession: noun + definite article + possessor after it (e.g., bíllinn hans, tölvan okkar, síminn hennar). English doesn’t do this, but in Icelandic it’s the default.

Can I say Hennar sími er bilaður?

Yes. Preposing the possessive is grammatical and tends to add emphasis or contrast (HER phone, not someone else’s). When preposed, you normally don’t use the definite ending on the noun: hennar sími. The everyday, most neutral version is still síminn hennar.

Can I drop the definite article and say Sími hennar er bilaður?

It’s possible and appears in careful or written styles, but in everyday speech síminn hennar is more idiomatic. Without the article, it can feel a bit more generic or non-unique (“a phone of hers”) depending on context.

Why is it síminn and not símann or síma?

Because it’s the subject, so it’s nominative singular definite: síminn.

símann = accusative singular definite (e.g., as a direct object).
símanum = dative singular definite.
símans = genitive singular definite. (Indefinite singular oblique forms are síma.)

Why does the adjective end in -aður (bilaður)?

Adjectives agree with the noun’s gender, number, and case. Síminn is masculine nominative singular, so the adjective is bilaður (m). Other forms:

Feminine: biluð (e.g., Tölvan hennar er biluð).
Neuter: bilað (e.g., Sjónvarpið hennar er bilað).

Can I use brotinn instead of bilaður?

Usually no.

bilaður = not working/out of order (typical for devices).
brotinn = broken in pieces/physically cracked or smashed.
Examples: Síminn er bilaður (won’t turn on); Skjárinn er brotinn (the screen is cracked).

What case is hennar, and does it change?

Hennar is the genitive of hún (“she”) used for possession. As a possessive, it’s invariable (it stays hennar regardless of the noun’s case):

Ég hringdi í símann hennar (accusative on the noun, hennar unchanged).
Related forms: hans (his), þeirra (their), also invariable.

Could I use the reflexive possessive sinn here?

Not in this sentence. Sinn refers back to a 3rd-person subject within the same clause. Here, the subject is síminn (“the phone”), so to say it belongs to a woman, use hennar.

Reflexive example (same-clause 3rd-person subject): Hún missti símann sinn (“She lost her [own] phone”).
With a subordinate clause: Hún segir að síminn hennar sé bilaður (you cannot use sinn there to refer to “her”).

What exactly is er?

It’s the 3rd person singular present of vera (“to be”). Present forms:

ég er; þú ert; hann/hún/það er; við erum; þið eruð; þeir/þær/þau eru.

How do you pronounce the sentence?

Approximate guide:

Síminn ≈ “SEE-minn” (long ee sound in sí; stress on the first syllable).
hennar ≈ “HEN-nar” (double n is clearly long).
er ≈ “air” with a tapped/trilled r.
bilaður ≈ “BEE-lah-thur” (ð like the th in “this”; final -ur with a short u like in “put”).
Icelandic stress is on the first syllable of each word.

How would I say similar sentences with other genders or people?

Masculine: Síminn hans er bilaður (“His phone is broken”).
Feminine: Tölvan hennar er biluð (“Her computer is broken”).
Neuter: Sjónvarpið þeirra er bilað (“Their TV is broken”).
Keep adjective agreement: bilaður (m), biluð (f), bilað (n).

How do I say “Her phone has broken down” (event) instead of the state “is broken”?

Use the verb bila for the event:

Simple past: Síminn hennar bilaði (“Her phone broke down”).
Present perfect: Síminn hennar hefur bilað (“Her phone has broken down”).
The original sentence with er bilaður describes the resulting state.