Penninn er brotinn.

The pen is broken.

Breakdown of Penninn er brotinn.

• vera: to be
• penninn: the pen
• brotinn: broken

Questions & Answers about Penninn er brotinn.

Why does penn become penninn?

Icelandic often expresses the by attaching a definite article suffix to the noun.

• penni = a pen (indefinite)
• penninn = the pen (definite)
  The base noun here is penni (masculine). In the nominative singular, penni + -inn → penninn.

What case is penninn in, and how can I tell?

Penninn is nominative singular because it is the subject of the sentence (the thing being described). Also, the verb er (from að vera, to be) links a subject to a description, so the subject stays in the nominative.

Why is the verb er used, and what does it mean grammatically?

Er is the 3rd person singular present tense form of að vera (to be). It agrees with the subject (penninn, he/it grammatically).
So: penninn er … = the pen is …

What is brotinn exactly—an adjective or a verb form?

Brotinn is historically a past participle (from brjóta, to break), but here it functions as a predicate adjective meaning broken. Icelandic commonly uses past participles like adjectives:

• Glugginn er lokaður = The window is closed
• Penninn er brotinn = The pen is broken

Why is it brotinn and not some other form like brotið or brotin?

Because Icelandic adjectives/participles must agree with the noun in gender, number, and case.
Penninn is masculine singular nominative, so the agreeing form is brotinn. Compare:

• Masculine sg. nom.: penninn er brotinn
• Feminine sg. nom.: bókin er brotin (the book is broken)
• Neuter sg. nom.: blaðið er brotið (the paper/sheet is broken/torn)
• Plural: pennarnir eru brotnir (the pens are broken)

Does brotinn have a “definite” form like adjectives sometimes do in Icelandic?

Yes. Icelandic adjectives often have a weak (definite) form when used with a definite noun, especially inside a noun phrase (like the broken pen) or after certain determiners. For predicate position (after er), many speakers still use the strong form as in your sentence.
You may also encounter Penninn er brotinn as the normal, neutral phrasing.

How would I say A pen is broken (indefinite) instead?

You would drop the definite suffix:

• Penni er brotinn. = A pen is broken.
  (You could also specify more context, because an indefinite subject like that can sound a bit “out of the blue” in some situations—similar to English.)

How do I make this sentence negative?

Put ekki after the verb:

• Penninn er ekki brotinn. = The pen is not broken.

How do I turn it into a yes/no question?

Invert the verb and the subject:

• Er penninn brotinn? = Is the pen broken?
  You can also add ekki for a negative question:
• Er penninn ekki brotinn? = Isn’t the pen broken?

What’s the pronunciation/stress pattern I should know for this sentence?

Icelandic stress is normally on the first syllable of a word:

• PENN-inn er BROT-inn
  Also note:
• nn is clearly pronounced (a long/strong n sound).
• o in brotinn is a short vowel (not like English broke).