Hurðarkarmurinn er mjór.

Because Icelandic makes very frequent use of compound nouns, and they are usually written as one word.

Here, hurðarkarmurinn is built like this:

• hurðar- = door-
• karmur = frame
• -inn = the

So the whole word means the door frame.

This is very normal in Icelandic. English often writes similar ideas as two words, but Icelandic usually prefers one compound word.

The first part of the compound comes from hurð (door), but in this compound it appears as hurðar-, which is based on the genitive singular form hurðar.

That is very common in Icelandic compounds: the first noun often appears in a genitive or genitive-like linking form.

So:

• hurð = a door
• hurðar- = door's / door-

Literally, the structure is something like door's frame, though in natural English we just say door frame.

It marks the noun as definite, meaning the.

In Icelandic, the definite article is usually attached to the end of the noun instead of being a separate word in front.

So:

• hurðarkarmur = a door frame
• hurðarkarmurinn = the door frame

The ending looks like -urinn here because the base noun is karmur, a masculine noun ending in -ur, and the definite form changes accordingly.

It is masculine.

A very useful rule in Icelandic compounds is that the last part usually decides the gender of the whole compound.

Here:

• hurð is feminine
• karmur is masculine
• therefore hurðarkarmur is masculine

That matters because adjectives must agree with the noun in gender, number, and case.

Because mjór is the masculine singular nominative form, and it agrees with hurðarkarmurinn.

In this sentence:

• hurðarkarmurinn = masculine
• singular
• nominative

So the adjective also appears in the matching form:

• mjór

A very important point: after vera (to be), Icelandic usually uses the adjective in its predicative form, which is typically the strong form.

So you say:

• Hurðarkarmurinn er mjór. = The door frame is narrow.

But when the adjective comes directly before the noun, you would normally use the weak form:

• mjói hurðarkarmurinn = the narrow door frame

That difference is one of the things English speakers often need to get used to.

It is in the nominative case, because it is the subject of the sentence.

The sentence structure is:

• Hurðarkarmurinn = subject
• er = verb
• mjór = predicate adjective

With vera (to be), the predicate adjective also appears in the nominative, so mjór matches the subject in case as well as gender and number.

Because this is the normal Icelandic pattern for a simple statement:

• Subject + verb + complement

So:

• Hurðarkarmurinn = the subject
• er = is
• mjór = narrow

That is the ordinary, neutral word order. Icelandic can move things around more than English in some contexts, but this sentence uses the standard basic order.

A rough learner-friendly approximation is:

HUR-thar-kar-mu-rin er myohr

A few useful notes:

• ð is like the th in this
• r is usually rolled or tapped
• ó is a long o sound
• mj- in mjór sounds roughly like my-

Don’t worry if your pronunciation is not perfect at first. The most useful thing is to notice the main sounds and stress pattern.

A few useful related forms are:

• hurðarkarmur = a door frame
• Hurðarkarmur er mjór. = A door frame is narrow / The door frame is narrow in an indefinite or more general sense
• hurðarkarmarnir = the door frames
• Hurðarkarmarnir eru mjóir. = The door frames are narrow

Notice the changes:

• singular er → plural eru
• singular adjective mjór → plural masculine mjóir

This shows the normal Icelandic agreement pattern very clearly.