Learn Hardcore Icelandic: Lyfin í apótekinu eru dýr, en höfuðverkurinn fer. - The medicines at the pharmacy are expensive, but the headache goes away.

Indefinite plural: lyf
Definite plural: lyfin
Singular definite would be lyfið (“the medicine”), but the sentence talks about multiple medicines, so it uses the plural.

Lyf looks the same in singular and plural. How can I tell this is plural?

From agreement:

The verb is eru (“are”), which is 3rd person plural.
The adjective is dýr, which here is the neuter plural form (see below). Compare:
Singular: Lyfið er dýrt. (“The medicine is expensive.”)
Plural: Lyfin eru dýr. (“The medicines are expensive.”)

Why is it í apótekinu and not í apótekið?

The preposition í takes:

Dative for location (being in/at): í apótekinu = “in the pharmacy”
Accusative for motion (into): í apótekið = “into the pharmacy” Your sentence describes location, hence dative singular definite: apóteki
- article → apótekinu.

What are the key forms of apótek so I can recognize apótekinu?

Core forms (neuter):

Nom/Acc sg: apótek
Dat sg: apóteki; Def dat sg: apótekinu
Def nom/acc sg: apótekið
Nom/Acc pl: apótek; Dat pl: apótekum
Def pl (nom/acc): apótekin; Def dat pl: apótekunum

Why is the adjective dýr used (and not dýrir, dýrar, or dýru)?

Adjectives in predicate position (after “to be”) take the strong inflection. For dýr (“expensive”):

Strong nominative plural: masculine dýrir, feminine dýrar, neuter dýr Since lyf is neuter plural, the correct form is dýr. Note: dýru is the weak form, used attributively with definites (e.g., dýru lyfin “the expensive medicines”), not in predicates after “to be.”

Why is it eru instead of er?

Because the subject Lyfin is plural. Present tense of vera (“to be”): ég er, þú ert, hann/hún/það er, við erum, þið eruð, þeir/þær/þau eru.

Is the verb really in second position (V2) here?

Yes. Icelandic main clauses are verb-second. The whole subject phrase Lyfin í apótekinu counts as one constituent; the finite verb eru is the next element. After the conjunction en, the new clause also has V2: höfuðverkurinn (subject) + fer (verb).

Do I need the comma before en?

Yes, standard punctuation puts a comma before en (“but”) when it connects two independent clauses. It’s similar to English usage.

Exactly what does en mean here, and could I use og instead?

en = “but” (contrast). og = “and” (addition). Swapping en for og would remove the contrast; the original emphasizes “pricey medicines, but the headache goes away.”

Why höfuðverkurinn (with -inn) and what case is it?

It’s nominative singular definite: höfuðverkur (m.) “headache” → höfuðverkurinn (“the headache”). It’s the subject of the clause, so nominative is required. The definite accusative would be höfuðverkinn, used for an object, not a subject.

I often see “Ég er með höfuðverk” rather than höfuðverkur. What’s the difference?

That’s an idiom: vera með + acc to express “have (a symptom)”. So:

Ég er með höfuðverk. = “I have a headache.” (accusative, indefinite) When the headache is the subject, you typically use the nominative form:
Höfuðverkurinn fer. = “The headache goes away.”

Does fer by itself really mean “go away”? What are alternatives?

Yes. fara can mean “leave/go away,” so Höfuðverkurinn fer is idiomatic. Other natural options:

Höfuðverkurinn hverfur. (“disappears”)
Höfuðverkurinn líður hjá. (“wears off, passes”)
Höfuðverkurinn gengur yfir. (“passes”)
Höfuðverkurinn fer burt. (“goes away” with explicit “away”)

Can I say “Lyfin eru dýr í apótekinu” instead? Does it change the meaning?

Yes, it’s grammatical. Subtle nuance:

Lyfin í apótekinu eru dýr restricts the set to “the medicines in the pharmacy.”
Lyfin eru dýr í apótekinu can be heard as “The medicines are expensive in the pharmacy (as opposed to elsewhere),” i.e., emphasizing location/contrast.

How would I say the generic “Medicine is expensive,” or “Medicine in pharmacies is expensive”?

Generic: Lyf eru dýr.
Generic with location: Lyf í apótekum eru dýr. (“Medicine in pharmacies is expensive”) Using singular “a pharmacy”: Lyf í apóteki eru dýr is possible but sounds less like a general truth.

Why is the adjective strong in the predicate but weak before a definite noun?

Rule of thumb:

Predicate after “to be”: strong inflection → Lyfin eru dýr.
Attributive before a definite noun: weak inflection → dýru lyfin (“the expensive medicines”) Compare: Dýr lyf (“expensive medicines,” strong, indefinite) vs dýru lyfin (weak, definite).

Any quick pronunciation tips for the sentence?

Stress is on the first syllable of each word: LY-fin í A-pó-te-ki-nu eru DÝR, en HÖ-fuð-verk-ur-inn fer.
ö like the vowel in French “peu.”
ð in höfuð- is like the “th” in “this.”
Final -inn in -urinn is a long “nn.”
fer rhymes roughly with English “fair” (shorter).