Stolen ser gammeldags ut.

Because stol means a chair, while stolen means the chair.

• en stol = a chair
• stolen = the chair

Norwegian often puts the definite article on the end of the noun instead of using a separate word like English the.

In Norwegian, the noun itself often carries the meaning of the.

So:

• stol = chair
• stolen = the chair

That ending -en is the definite ending for many masculine nouns.

A separate word such as den is usually not needed here. In fact, den stolen would normally mean something more like that chair, not simply the chair.

Ser ... ut means looks or appears.

So Stolen ser gammeldags ut means that the chair has an old-fashioned appearance.

This is a very common Norwegian pattern:

• Han ser trøtt ut = He looks tired
• Huset ser nytt ut = The house looks new
• Det ser bra ut = It looks good

Here, ut is part of the expression. It is not being translated literally as out.

Because with this expression, Norwegian normally uses the pattern:

subject + ser + adjective + ut

So:

• Stolen ser gammeldags ut
• Bilen ser dyr ut
• Hun ser glad ut

You can think of it as a fixed structure: se + description + ut.

Yes, you could, but the meaning is slightly different.

• Stolen ser gammeldags ut = The chair looks old-fashioned
• Stolen er gammeldags = The chair is old-fashioned

The version with ser ... ut talks about appearance.
The version with er sounds more direct, as if you are stating it as a fact.

In many situations, both are possible, but ser gammeldags ut is often the more natural choice when you are describing how something looks.

Gammeldags means old-fashioned.

It usually describes something that seems to belong to an earlier style or period. Depending on context, it can be:

• neutral
• positive, like charming or traditional
• negative, like outdated

So this sentence does not necessarily mean the chair is physically old. It means the chair has an old-fashioned style or appearance.

Because gammel and gammeldags are not the same word.

• gammel = old
• gammeldags = old-fashioned

So:

• Stolen er gammel = The chair is old
• Stolen ser gammeldags ut = The chair looks old-fashioned

A chair can be gammel without being gammeldags, and it can look gammeldags even if it is new.

Sometimes, but in this sentence the form gammeldags is correct as it stands.

With this singular subject, you use gammeldags.
In plural, you will often see gammeldagse.

For example:

• en gammeldags stol = an old-fashioned chair
• stolen ser gammeldags ut = the chair looks old-fashioned
• gammeldagse stoler = old-fashioned chairs
• stolene ser gammeldagse ut = the chairs look old-fashioned

So yes, the adjective can vary, but not every sentence will show that clearly.

Here are some useful comparisons:

• Stolen ser gammeldags ut = The chair looks old-fashioned
• Bordet ser gammeldags ut = The table looks old-fashioned
• Stolene ser gammeldagse ut = The chairs look old-fashioned

So the noun changes depending on gender and number:

• en stol → stolen
• et bord → bordet
• stoler → stolene

And the adjective may also change in the plural: gammeldagse.

Not exactly.

Norwegian stolen is the noun stol plus the definite ending -en. It is not related to the English past participle stolen.

A rough pronunciation guide is:

• stol: the vowel is long, roughly like oo in food
• stolen: something like STOO-len, with the stress on the first syllable

The exact pronunciation depends a bit on dialect, but it definitely does not sound like the English verb form stolen.