Learn Hardcore Norwegian: Oslo er størst.

Oslo er størst. – No noun, no separate “the”.
den største byen – With a noun, you show definiteness using den … -ste (the biggest city).

What’s the difference between stor, større, and størst?

They’re the three degrees of the adjective stor (big):

stor – positive: big
- Oslo er stor. – Oslo is big.
større – comparative: bigger
- Oslo er større enn Bergen. – Oslo is bigger than Bergen.
størst – superlative: biggest
- Oslo er størst. – Oslo is the biggest.

So Oslo er størst is saying that, in some comparison (often “of the cities in Norway”), Oslo is at the very top: it’s the biggest one.

When do I use størst and when do I use største?

Very roughly:

størst – usually stands alone, often after er:
- Oslo er størst. – Oslo is (the) biggest.
- Hvem er størst? – Who is (the) biggest?
- Størst mulig – as big as possible.
største – usually comes before a noun, often with den/det/de or a possessive:
- den største byen – the biggest city
- de største byene – the biggest cities
- min største feil – my biggest mistake

In Oslo er størst, the adjective is predicative (after er and not before a noun), so you use størst, not største.

Does the verb er change depending on who or what the subject is, like “is/are/am” in English?

No. Er is the present tense of å være (to be), and it is the same for all subjects:

jeg er – I am
du er – you are
han/hun er – he/she is
vi er – we are
dere er – you (plural) are
de er – they are
Oslo er størst. – Oslo is the biggest.

So you never have to choose between “am/is/are” in Norwegian: you just use er for the present tense.

How do you pronounce størst, especially the letter ø?

A simple approximation:

størst ≈ “stursht”, with a very short vowel.

Details:

ø: A rounded vowel, a bit like the vowel in English “bird” (British), but with your lips rounded.
rs: In many Norwegian accents, r + s becomes a “sh” sound. So størst sounds more like “størsht” than “størst” with a clear s.
The final t is usually pronounced in standard Eastern Norwegian.

IPA (approx.): [stœʂt].

Is størst an adjective here? How can an adjective stand alone without a noun?

Yes, størst is an adjective in Oslo er størst.

There are two main ways adjectives are used:

Attributive – directly before a noun:
- en stor by – a big city
- den største byen – the biggest city
Predicative – after a linking verb like er (is/are), blir (becomes):
- Oslo er stor. – Oslo is big.
- Oslo er størst. – Oslo is biggest.

In predicative position, the adjective does not need to be followed by a noun; it simply describes the subject. So Oslo er størst is perfectly normal, just like “Oslo is biggest” would be grammatically fine (even if English usually prefers “the biggest”).

Could I say Oslo er veldig stor instead? Does it mean the same as Oslo er størst?

They don’t mean the same thing:

Oslo er veldig stor.
– Oslo is very big.
This just describes Oslo’s size, with no comparison.
Oslo er størst.
– Oslo is the biggest.
This is a superlative: it compares Oslo to others and says it’s number one in size.

So veldig stor = “very big”, while størst = “biggest (of the group)”.

If I want to ask “Is Oslo the biggest?”, how do I form the question in Norwegian?

You simply put the verb first:

Er Oslo størst? – Is Oslo the biggest?

In Norwegian yes/no questions:

There is no “do” like do/does/did in English.
You usually just invert subject and verb:
- Oslo er størst. – Oslo is biggest.
- Er Oslo størst? – Is Oslo biggest?

The rising intonation and the question mark show that it’s a question.

“Biggest what?” How is that understood in Norwegian if you only say Oslo er størst?

Exactly like in English: it’s understood from context.

You often add extra information:

Oslo er størst i Norge. – Oslo is the biggest in Norway.
Oslo er størst av de tre byene. – Oslo is the biggest of the three cities.

But if the context is already clear—for example, everyone is talking about Norwegian cities—then:

Oslo er størst.

is enough, just like saying “Oslo is the biggest.” in English when everyone knows you mean the biggest city in Norway, etc.

Does størst change form depending on gender or number, like with other adjectives?

In this use (predicative superlative, after er), størst stays the same for all genders and numbers:

Oslo er størst. – Oslo is biggest.
Byen er størst. – The city is biggest.
Husene er størst. – The houses are biggest.

There is no størst / størst / største variation here; it’s just størst.

The form største is used mainly before nouns:

den største byen – the biggest city
de største husene – the biggest houses

So:

After er (no noun): størst
Before a noun (with article/possessive): største

Can I drop er and just say Oslo størst, like in some other languages?

Not in normal Norwegian sentences.

Norwegian generally needs a verb in a complete sentence, so you say:

Oslo er størst.

You might see “Oslo størst” in headlines or very telegraphic notes (like a newspaper title), but that is headline style, not standard full-sentence grammar in speech or writing.

What are the dictionary (base) forms of er and størst?

er is the present tense of the verb å være – to be.
- Infinitive: å være
- Present: er
- Past: var
- Past participle: vært
størst is the superlative of the adjective stor – big.
- Positive: stor – big
- Comparative: større – bigger
- Superlative: størst (short form), største (inflected/attributive form)

So Oslo er størst literally uses å være in the present and stor in its superlative form.