Learn Hardcore Icelandic: Ég hef búið í borginni lengi, en núna langar mig að flytja í sveitina. - I have lived in the city for a long time, but now I want to move to the countryside.

In Icelandic, just like in English, when you mention how long something has been true up to now, you normally use the present perfect, not the simple present:

Ég bý í borginni.
= I live in the city. (simple fact about now)
Ég hef búið í borginni lengi.
= I have lived in the city for a long time. (emphasizes duration up to now)

So Ég bý í borginni is correct by itself, but when you add lengi (for a long time), the natural tense is Ég hef búið.

What exactly is búið here? Is it an adjective, a verb form, or something else?

búið is the past participle of the verb að búa (to live, to reside).

The important pieces:

Infinitive: að búa – to live / reside
1st person singular present: ég bý – I live
Past participle (neuter form): búið – used with the auxiliary hafa (to have) to form the perfect.

So:

Ég hef búið = I have lived / I have been living

Unlike English, Icelandic participles agree in gender/number/case when used as adjectives, but with the auxiliary verb (hef, hefur, hafa, etc.) they simply make a perfect tense, like English have + past participle.

Why is it í borginni but í sveitina? Why are the endings different?

This is a very common and important pattern with the preposition í (in / into).

í + dative is used for a location (where something is).
í + accusative is used for motion/direction (where something is going to).

In the sentence:

í borginni – in the city
→ static location (where I have been living)
→ dative with definite article: borgin (the city) → dative singular borginni.
í sveitina – to the countryside
→ motion towards a place (where I want to move to)
→ accusative with definite article: sveitin (the countryside) → accusative singular sveitina.

So the difference in endings (-inni vs -ina) tells you:

The noun is definite (the city, the countryside),
Whether the case is dative (location) or accusative (direction).

Why is it borginni and not just borg? How is “the city” expressed?

Icelandic usually does not use a separate word for “the”. Instead, the definite article is attached to the end of the noun as a suffix and may also trigger a case ending.

For the feminine noun borg (city), singular forms are:

Nominative: borgin – the city (subject)
Accusative: borgina – the city (object)
Dative: borginni – the city (e.g. after í for location)
Genitive: borgarinnar

So:

í borg = in a city (indefinite, and also wrong case for location here)
í borginni = in the city (definite + correct dative case for location)

In the sentence, the speaker clearly means the city they’ve been living in, not just any city, so borginni (with the definite article and correct case) is used.

Why is it langar mig and not langar ég? Isn’t “I” the subject?

The verb að langa (to want, to long for) is impersonal in Icelandic. That means the person who wants something is not the grammatical subject.

The experiencer (“me”) is in the accusative: mig.
The verb appears in 3rd person singular: langar.
If you mention what you want, that thing is in the nominative and is the grammatical subject.

Basic pattern:

Mig langar í ís.
Literally: Me (acc.) longs for ice cream (nom.).
Natural English: I want ice cream.

In the sentence:

núna langar mig að flytja í sveitina
Literally: now longs me to move to the countryside
Natural: but now I want to move to the countryside.

So mig is accusative (object-like role), and langar stays 3rd person singular. Using ég langa is ungrammatical.

Can I say núna mig langar instead of núna langar mig?

No, that word order is wrong in Icelandic.

In main clauses, Icelandic normally has verb-second word order:

Some element (subject, adverb, etc.) in first position,
Then the finite verb,
Then the rest (subject/objects/etc.).

In your sentence, núna (now) is first, so the verb must immediately follow:

Núna langar mig að flytja í sveitina. ✅
(núna = 1st position, langar = 2nd position)

If you move núna later, you can have:

Mig langar núna að flytja í sveitina. ✅
(now is not in first position, so it doesn’t trigger verb-second)

But:

Núna mig langar … ❌
breaks the verb-second rule.

What is the role of að before flytja?

að here is the infinitive marker, similar to English “to” before a verb.

að flytja = to move (infinitive)
mig langar að flytja = I want to move

So the structure is:

langar mig að + infinitive
= I want to + verb

You need að before an infinitive verb in this kind of construction, so mig langar flytja without að is incorrect.

What does flytja mean exactly, and is it only “to move house”?

að flytja is versatile. Common meanings include:

to move (house), relocate
- Ég ætla að flytja í sveitina. – I’m going to move to the countryside.
to transport, carry, deliver
- að flytja vörur – to transport goods
to perform / deliver (a speech, a piece of music)
- að flytja fyrirlestur – to deliver a lecture
- að flytja lag – to perform a song

In the given sentence, from context (í sveitina), it clearly means to move (to live somewhere else).

Why is it í sveitina and not also í sveitinni like í borginni?

The difference is not about the place itself but about the meaning of the preposition + case:

í borginni – in the city (location, no movement) → dative
í sveitina – to the countryside (movement towards) → accusative

If you were just talking about already being in the countryside, you would use the dative:

Ég bý í sveitinni. – I live in the countryside. (location)

But because the sentence expresses moving to the countryside, you must use accusative:

Ég ætla að flytja í sveitina. – I’m going to move to the countryside.

So borginni vs sveitina reflects location vs direction, not a difference like “city” vs “countryside” in definiteness.

What does lengi do here, and can it go somewhere else in the sentence?

lengi means “for a long time” / “for long” and modifies the whole clause hef búið í borginni.

Ég hef búið í borginni lengi
= I have lived in the city for a long time.

You can move lengi a bit without changing the meaning much, as long as it stays in the first clause:

Ég hef lengi búið í borginni.
Lengi hef ég búið í borginni. (more poetic/emphatic)

But you would not normally put it into the second clause, because it clearly refers to how long you have lived in the city, not to wanting to move.

Can I say Ég bý í borginni lengi to mean “I have lived in the city for a long time”?

No, that sounds wrong in modern Icelandic.

To express duration up to now, you use the present perfect:

Ég hef búið í borginni lengi. ✅
= I have lived in the city for a long time.

Ég bý í borginni lengi would be interpreted (if at all) more like a habitual or future-like statement (e.g., “I live in the city for long periods”), but it’s not a natural way to say what you mean. Stick to hef búið with lengi for “have lived for a long time”.

What’s the difference between Ég hef búið í borginni lengi and Ég bjó í borginni lengi?

They differ in tense and implication about the present:

Ég hef búið í borginni lengi.
- Present perfect.
- I have lived in the city for a long time (and I still do, up to now).
Ég bjó í borginni lengi.
- Simple past.
- I lived in the city for a long time (but I don’t live there now).

In your full sentence:

Ég hef búið í borginni lengi, en núna langar mig að flytja í sveitina.
= I have lived in the city for a long time, but now I want to move to the countryside.
→ Emphasizes your long stay up to the present and your new desire.

If you said Ég bjó í borginni lengi, it would suggest that time in the city is already fully in the past.