Learn Hardcore Norwegian: Beskrivelsen i brevet er uklar, så jeg sender øyeblikkelig en e-mail og spør. - The description in the letter is unclear, so I immediately send an email and ask.

You use i here because the description appears inside the letter (in its content).
på brevet would mean on the letter (on the surface), which would be odd for this meaning.

Why is it Beskrivelsen i brevet er uklar and not Beskrivelsen er uklar i brevet?

Both are grammatically possible, but they sound different:

Beskrivelsen i brevet er uklar
- Neutral, natural order.
- First identifies which description (the one in the letter), then comments on it: it is unclear.
Beskrivelsen er uklar i brevet
- Sounds like you’re contrasting different places:
  - The description is unclear *in the letter, (but maybe clear somewhere else).*
- Less natural if you just want to say that the description in the letter is unclear.

So the original sentence is the default, unmarked word order.

What does uklar mean, and why isn’t it uklart or uklare here?

uklar means unclear / vague / not well defined.

Adjectives in Norwegian agree with the noun’s gender/number and definiteness:

en uklar beskrivelse (masculine/feminine singular indefinite)
et uklart brev (neuter singular indefinite)
uklare beskrivelser (plural)
den uklare beskrivelsen (definite, masc./fem.)

In the sentence, the pattern is:

Beskrivelsen … er uklar.
- Subject: beskrivelsen (masc./fem. singular)
- Predicative adjective: uklar, matching that gender/number.

So uklar is correct here.

Why is there a comma before så, and what exactly does så mean here?

Here så is a coordinating conjunction meaning so / therefore, connecting two main clauses:

Beskrivelsen i brevet er uklar,
så jeg sender øyeblikkelig en e-mail og spør.

Because it connects two independent clauses, Norwegian normally uses a comma before så in this function.

så has several uses; two important ones:

Coordinating conjunction (like here):
- Det regner, så jeg blir hjemme. = It’s raining, so I’m staying home.
Adverb meaning then / so in a sequence:
- Jeg spiser, så går jeg. = I eat, then I go.
- Word order after this adverb follows the V2 rule (verb in second position).

In this sentence, you should understand it as so / therefore.

Why is it så jeg sender and not så sender jeg?

Because så here is a conjunction, not an adverb.

As a conjunction (so/therefore), it introduces a new main clause with normal subject–verb order:
- …, så jeg sender … (subject jeg, then verb sender)
As an adverb meaning then/so, Norwegian uses verb‑second word order after it:
- Så sender jeg en e-mail. = Then I send an email.

So så jeg sender fits the “because A, so B”/”A, therefore I do B” structure.

What does øyeblikkelig mean, and how formal/common is it?

øyeblikkelig means immediately / at once.

øyeblikkelig – neutral; slightly formal or written-sounding.
Very common spoken alternatives:
- med en gang = right away
- straks = immediately / shortly

You could also say:

… så jeg sender med en gang en e‑post og spør.
… så jeg sender straks en e‑post og spør.

All mean essentially the same thing here.

Can you change the word order to jeg sender en e-mail øyeblikkelig? Does it sound different?

Yes, you can say both:

jeg sender øyeblikkelig en e-mail
jeg sender en e-mail øyeblikkelig

Both are correct. The difference is very small:

sender øyeblikkelig en e-mail
- Slightly more focus on the immediacy of the action.
sender en e-mail øyeblikkelig
- Slightly more focus on the thing you send, with øyeblikkelig added as extra info.

In everyday use, they’re almost interchangeable.

Why is it en e-mail and not ei or et? And is e-mail the normal word in Norwegian?

e-mail is treated as a masculine noun here, so you get:

en e‑mail = an email

However, the more common and more “Norwegian” word is e-post:

en e-post = an email (message)
e‑mail (with English spelling) is understood but less natural in modern Norwegian.

Norwegian masculine nouns typically use en:

en bil (a car)
en e‑post (an e‑mail)

Some dialects use ei for feminine nouns, but en is safe and standard in Bokmål.

Why can spør stand alone without an object? In English we’d say “ask about it.”

In Norwegian, if it is clear from context what you’re asking about, you can leave out the object:

Jeg spør. = I ask (about it / about that).
Jeg spør henne. = I ask her.
Jeg spør om det. = I ask about it.

In the sentence, it’s obvious that jeg spør refers to asking about the unclear description in the letter, so Norwegian doesn’t need to repeat om det or dem etc.

More explicit versions would be:

… og spør om beskrivelsen.
… og spør hva det betyr.

Why is sender in the present tense if the meaning is more like “I will send”?

Norwegian often uses the present tense for near future actions, especially when there is an adverb that indicates time:

Jeg sender øyeblikkelig en e‑post.
= I will send / I’m sending an e-mail immediately.
Jeg reiser i morgen.
= I’m leaving tomorrow.

You can use a future construction:

Jeg skal sende en e‑post øyeblikkelig.

But with øyeblikkelig, the simple present already clearly expresses a planned/near-future action.

Could I use fordi instead of så? What would be the difference?

Yes, but it changes which clause is cause and which is result.

Original:

Beskrivelsen i brevet er uklar, så jeg sender øyeblikkelig en e‑mail og spør.
- Cause: The description is unclear.
- Result: I send an email immediately and ask.

With fordi (because), you’d normally flip the order:

Jeg sender øyeblikkelig en e‑mail og spør fordi beskrivelsen i brevet er uklar.
= I send an email immediately and ask because the description in the letter is unclear.

So:

så = so / therefore (introduces the result).
fordi = because (introduces the reason).

What is the difference between brev and brevet?

brev is a neuter noun meaning letter.

et brev = a letter
brevet = the letter
brev (no ending) also works as plural letters in the indefinite plural:
- brev = letters (context decides)
- brevene = the letters

In the sentence, i brevet means in the letter (a specific letter just mentioned or known from context).

How would this sentence typically be said in casual modern Norwegian?

A very natural, everyday version could be:

Beskrivelsen i brevet er uklar, så jeg sender en e‑post med en gang og spør.

Here the changes are:

e‑post instead of e‑mail (more Norwegian).
med en gang instead of øyeblikkelig (very common spoken phrase).