Learn Hardcore Norwegian: Dette er en hemmelig gave, så ikke si noe. - This is a secret present, so don’t say anything.

Yes. Det er en hemmelig gave is perfectly natural and neutral; Dette er en hemmelig gave sounds a bit more pointed, as if you’re indicating something present or just introduced. If you want to say “This gift is secret,” use the definite form: Denne gaven er hemmelig (this specific gift, as subject).

Why is it en hemmelig gave and not et hemmelig gave?

Because gave is a common-gender noun in Bokmål, so its indefinite article is en: en gave (definite: gaven). Using et would be for neuter nouns (e.g., et brev). Note: ei gave is also allowed in Bokmål, but it’s more dialectal; en gave is the most standard.

Why is the adjective hemmelig not hemmelige or hemmeligt here?

Indefinite singular common gender uses the base form: en hemmelig gave.
Definite singular and all plural take -e: den hemmelige gaven, hemmelige gaver.
For neuter singular, many adjectives add -t, but adjectives ending in -ig/-lig do not: et hemmelig brev (not “hemmeligt”).
“Hemmeligt” is Danish spelling, not Norwegian.

What does så mean here?

Here så is a linking word meaning “so/therefore,” introducing a consequence: Dette er en hemmelig gave, så … = “This is a secret gift, so …”. It’s not the “so (very)” intensifier (as in “so big”), nor the purely temporal “then.” You could also use derfor (“therefore”): Dette er en hemmelig gave, derfor må du ikke si noe.

Is the comma before så necessary?

Yes, it’s standard to use a comma before så when it links two independent clauses (even if the second is an imperative): …, så ikke si noe. Without the comma it looks less standard and can be harder to read.

Why is it Ikke si noe and not Si ikke noe? Where does ikke go in negative imperatives?

The most natural placement is before the verb: Ikke si noe. You can also put it after for a slightly more formal/written feel or when there’s an object pronoun: Si ikke noe, Si det ikke til noen. All are grammatical; initial Ikke is the most common in speech.

Can I use ingenting or noe som helst instead of noe?

Yes, with nuances:

Ikke si noe = don’t say anything (neutral).
Ikke si ingenting is also used and feels a bit stronger (literally “say nothing”).
Ikke si noe som helst adds emphasis: “don’t say anything at all.”
All three are fine; the last two sound more emphatic.

What’s the difference between noe and noen?

noe = “something/anything” (things, abstract stuff): ikke si noe.
noen = “someone/anyone” (people) or “any/some” with countable plural nouns. To include the listener target, say: Ikke si det til noen (“Don’t tell anyone”).

Why use si and not fortelle? Aren’t both “to tell”?

Both exist but differ in usage:

si = “say,” often followed by what is said: si noe, si at …
fortelle = “tell,” typically with a recipient or a story: fortelle noen noe, fortelle om …
Here you could say: Ikke fortell det til noen (“Don’t tell it to anyone”) or stick with Ikke si noe (“Don’t say anything”).

Could I make the noun definite, like den hemmelige gaven?

Yes, but it changes focus. En hemmelig gave introduces the gift as one of many possible gifts. Den hemmelige gaven refers to a specific gift both speaker and listener can identify: Dette er den hemmelige gaven (“This is the secret gift”). Alternatively: Denne gaven er hemmelig (“This gift is secret”).

How do I pronounce the sentence?

Approximate IPA (Eastern Norwegian):

Dette [ˈdɛtːə]
er [æːr] or [eːr]
en [ɛn]
hemmelig [ˈhɛmːəli]
gave [ˈɡɑːʋə]
så [soː]
ikke [ˈɪkːə]
si [siː]
noe [ˈnuːə]
Smooth version: [ˈdɛtːə æːr ɛn ˈhɛmːəli ˈɡɑːʋə, soː ˈɪkːə siː ˈnuːə].

Are there natural alternative ways to say the second part (“so don’t say anything”)?

Yes, for example:

… så si ingenting.
… så ikke si det til noen.
… så hold det for deg selv. (“keep it to yourself”)
… så ikke røp det. / … så ikke avslør det. (“don’t reveal it”)
More formal: … derfor må du ikke si noe.