Sollyset gjør stuen lysere.

Gjør is the present tense of the verb å gjøre, which means to do / to make.

In this sentence, gjør corresponds to English makes:

• Sollyset gjør stuen lysere.
  The sunlight makes the living room brighter.

So the structure is:

• å gjøre – to do / to make
• gjør – does / makes (present tense)

Sollyset is one word because Norwegian likes compound nouns.

• sol = sun
• lys = light
• sollys = sunlight

Sollys is a neuter noun.
Its forms are:

• indefinite: sollys = sunlight
• definite: sollyset = the sunlight

In the sentence, sollyset means the sunlight (specific sunlight that is shining in).

• sollys = sunlight (general, indefinite)

  • e.g. Jeg liker sollys. – I like sunlight.

• sollyset = the sunlight (definite)

  • e.g. Sollyset gjør stuen lysere. – The sunlight makes the living room brighter.

So -et is the definite ending for neuter nouns.

The basic form (indefinite) is en stue = a living room / lounge.

Stuen is the definite singular:

• en stue – a living room
• stuen – the living room

So in the sentence:

• stuen = the living room

Both mean the living room and are correct in Bokmål:

• stuen – more formal/standard written Bokmål
• stua – more colloquial/spoken style (historically the feminine form)

You could see:

• Sollyset gjør stuen lysere. – neutral/standard style
• Sollyset gjør stua lysere. – slightly more informal / spoken feel

In this sentence, lys is an adjective meaning light / bright.

• base form: lys = light / bright
• comparative: lysere = lighter / brighter
• superlative: lysest = lightest / brightest

So lysere means brighter:

• stuen lysere = the living room (is) brighter

Both exist, but they emphasize slightly different things:

• lysere = brighter (comparative adjective: change in brightness)

  • Sollyset gjør stuen lysere. – The sunlight makes the living room brighter.

• mer lys = more light (more quantity of light, noun)

  • Sollyset gir mer lys i stuen. – The sunlight gives more light in the living room.

In your sentence, we are describing a quality of the room (how bright it is), so lysere is natural.

Norwegian is a V2 language in main clauses: the finite verb usually comes in second position.

Here:

1. Sollyset – subject (first element)
2. gjør – verb (second element)
3. stuen – object
4. lysere – object complement (describes how the object ends up)

The structure is:

• [Subject] [Verb] [Object] [Complement]
• Sollyset gjør stuen lysere.
  The sunlight makes the living room brighter.

You cannot move gjør away from the second position in a normal main clause.

Yes, that’s a very natural alternative:

• Stuen blir lysere av sollyset.
  The living room becomes brighter from the sunlight / because of the sunlight.

Differences:

• gjør-sentence: Sollyset gjør stuen lysere.
  – focuses on the sunlight actively causing the change.

• blir-sentence: Stuen blir lysere av sollyset.
  – focuses on the living room changing (becoming) brighter, and mentions the sunlight as the cause.

Meaning is very close; both are correct.

Gjør is present tense.

Main forms of å gjøre (to do / to make):

• infinitive: å gjøre – to do / to make
• present: gjør – do/does, make/makes
• preterite (past): gjorde – did / made
• past participle: gjort – done / made

Example:

• Sollyset gjør stuen lysere. – present
• I går gjorde sollyset stuen lysere. – past

No. In Norwegian, common nouns are not capitalized, just like in English.

• At the start of a sentence: Sollyset (capital S because it’s first word)
• In the middle of a sentence: sollyset, stuen, sollys, stue

So writing Sollyset gjør stuen lysere. is correct only because it starts the sentence; otherwise it would be sollyset.

Very roughly (using English-like hints):

• sollyset ≈ SOOL-lee-set

  • so like so in sofa, but longer oo sound
  • ll is doubled but not strongly pronounced
  • y is like German ü or French u (fronted); English learners often say something between ee and u.

• gjør ≈ yur (one syllable)

  • gj here sounds like a soft “y”
  • IPA: /jøːr/

• stuen ≈ STOO-en

  • u is like long oo in food
  • two syllables: stu-en

• lysere ≈ LEE-seh-reh

  • ly again has that front y vowel
  • three syllables: ly-se-re

Yes, that’s another natural variant:

• Sollyset lyser opp stuen.
  = The sunlight lights up the living room.

Nuance:

• gjør stuen lysere – focuses on the resulting brightness (brighter than before)
• lyser opp stuen – focuses on lighting up / illuminating the room

Both describe the effect of sunlight, but with slightly different imagery.