Learn Hardcore Icelandic: Við erum ekki sammála um hvort það sé betra fyrir umhverfið að búa í borg eða í sveit. - We do not agree on whether it is better for the environment to live in a city or in the countryside.

Sé is the subjunctive form of vera (to be). Icelandic often uses the subjunctive in indirect questions and in clauses expressing uncertainty, doubt, or something that’s being considered hypothetically.

Er = indicative: stating a fact
- Það er betra... – It is better... (as a fact)
Sé = subjunctive: considering or discussing whether something might be true
- hvort það sé betra... – whether it is better...

Because the main clause says Við erum ekki sammála um hvort... (we don’t agree about whether...), the statement inside hvort is not presented as a fact, so Icelandic naturally uses the subjunctive sé.

What exactly does hvort mean here, and how is it different from ef?

In this sentence, hvort introduces an indirect question and corresponds to English whether:

...um hvort það sé betra...
→ ...about whether it is better...

Key points:

hvort ... eða ... = whether ... or ...
- hvort það sé betra ... að búa í borg eða í sveit
  → whether it is better ... to live in a city or in the countryside
hvort is used:
- in yes/no questions (direct or indirect)
- when you have alternatives: hvort A eða B
ef usually means if (a condition), not whether:
- Ef það er betra ... þá gerum við það.
  If it is better ... then we’ll do it. (conditional)

You cannot replace hvort with ef in this sentence; ef would sound like a conditional, not “whether.”

What is the function of það in hvort það sé betra fyrir umhverfið að búa...? Is it just a dummy “it”?

Yes, here það works very much like dummy “it” in English:

The real content is að búa í borg eða í sveit (to live in a city or in the countryside).
það stands in as the grammatical subject of sé betra.

You can think of it as:

hvort það sé betra (fyrir umhverfið) að búa í borg eða í sveit
→ whether it is better (for the environment) to live in a city or in the countryside

In more abstract clauses like this, Icelandic usually keeps það, although you might sometimes see hvort sé betra... without það in more formal or compact style. In everyday speech, hvort það sé... is very natural.

What kind of word is sammála, and how is it used? Why do we say Við erum ekki sammála?

Sammála behaves like an adjective meaning in agreement or of the same opinion.

vera sammála (e-m / um e-ð)
- to agree (with someone / about something)

In your sentence:

Við erum ekki sammála
→ We do not agree / We are not in agreement

A few important points:

Sammála is used predicatively (after vera):
- Við erum sammála. – We agree.
- You generally do not use it as an attributive adjective before a noun
  (you don’t say *sammála fólk for people who agree).
You can have:
- sammála um eitthvað – agree about something
  Við erum sammála um þetta. – We agree about this.
- sammála e-m – agree with someone
  Ég er sammála þér. – I agree with you.
There is also ósammála = in disagreement:
- Við erum ósammála. – We disagree.

In your sentence they chose ekki sammála instead of ósammála, but both are common:

Við erum ekki sammála um hvort...
Við erum ósammála um hvort...
Both mean We do not agree / We disagree about whether...

What does um do in sammála um hvort það sé betra...? Could it be left out?

Here um is a preposition meaning about / concerning:

sammála um eitthvað – to agree about something
ósammála um eitthvað – to disagree about something

In the sentence:

Við erum ekki sammála um hvort það sé betra...
→ We don’t agree about whether it is better...

You cannot just drop um here; it’s part of the normal construction sammála um + clause/thing. Without um, it would sound incomplete or wrong in this context.

Does ekki negate sammála or the whole subordinate clause? How should I understand Við erum ekki sammála um hvort...?

Grammatically, ekki is placed with the verb in the main clause:

Við erum ekki sammála...
We are not in agreement...

So what is negated is being in agreement, not the content of the hvort clause itself.

Compare:

English: We don’t agree about whether it is better...
(same structure: the not belongs to agree, not to it is better.)

The embedded clause hvort það sé betra fyrir umhverfið að búa í borg eða í sveit is just the topic they disagree about. The sentence is not saying “it is not better” – only that they are not in agreement about the question.

Why is umhverfið definite (-ið) in fyrir umhverfið? In English we usually just say “for the environment” without a definite article.

In Icelandic, the definite form is often used for general, collective or abstract nouns where English might omit the article or use a bare singular/plural.

umhverfið = the environment (in general)
fyrir umhverfið ≈ for the environment (meaning “for the environment in general / for the environment as a whole”)

Similar patterns:

náttúran – nature
loftið – the air (in general)
jörðin – the Earth

So fyrir umhverfið here is perfectly idiomatic and means for the environment in general, not for some particular environment.

Why is að búa used here instead of something like að lifa?

Icelandic distinguishes between:

búa – to live, reside, dwell (somewhere)
lifa – to live, be alive (biological life or lifestyle)

In your sentence the focus is on where you live:

að búa í borg eða í sveit
→ to live / reside in a city or in the countryside

Using lifa here would sound wrong, as if you were talking about the act of being alive in a city vs. in the countryside. For location of residence, búa is the natural verb.

Why are borg and sveit in the dative (í borg, í sveit)?

The preposition í can take either accusative or dative, depending on meaning:

Accusative with motion into something:
- Ég fer í borgina. – I go to the city.
Dative with location / being in something:
- Ég bý í borginni. – I live in the city.

In your sentence, að búa (to live, reside) describes a location, not movement, so í takes the dative singular:

í borg (dative of borg) – in a city
í sveit (dative of sveit) – in the countryside

That’s why you see the bare dative forms there.

Why don’t we say í borginni or í sveitinni (with the definite article) like “in the city / in the countryside”?

English often uses the city / the countryside in a generic sense, but Icelandic is more likely to leave these nouns indefinite when speaking generally:

að búa í borg – to live in a city / in the city (as a type of place)
að búa í sveit – to live in the countryside

Using the definite forms í borginni, í sveitinni usually makes the reference more specific, as if you meant a particular city or a particular (known) rural area:

Ég bý í borginni. – I live in the city (often “in the city we both know / the local city”).
Ég bý í sveitinni. – I live out in the countryside (often specific or familiar).

Here, the sentence contrasts urban vs. rural living in general, so í borg and í sveit without the article are natural.

Why is í repeated: að búa í borg eða í sveit, and not just að búa í borg eða sveit?

Both are possible, but repeating the preposition í is:

very common in careful or written style
clearer and more balanced, especially when the two options are somewhat contrasting (borg vs sveit)

So:

að búa í borg eða í sveit – fully explicit, stylistically smooth
að búa í borg eða sveit – still understandable, but can sound a bit lighter or less formal

Repeating í makes it easy to parse: to live in (a) city or in (the) countryside.

How is the long clause hvort það sé betra fyrir umhverfið að búa í borg eða í sveit structured grammatically?

That whole chunk is a subordinate noun clause introduced by hvort, and it functions as the object of sammála um:

Main clause:
Við erum ekki sammála um [ X ].
Subordinate clause X:
hvort það sé betra fyrir umhverfið að búa í borg eða í sveit

Inside X:

hvort – introduces an indirect question: whether
það – dummy subject of sé betra
sé – subjunctive of vera
betra – comparative of góður (better)
fyrir umhverfið – prepositional phrase: for the environment
að búa í borg eða í sveit – infinitive phrase explaining what is better:
- að búa – to live / reside
- í borg – in a city
- eða í sveit – or in the countryside

So structurally, it matches the English pattern:

We do not agree about *whether it is better for the environment to live in a city or in the countryside.*