Learn Hardcore Norwegian: Vi kjøper to lyspærer og skrur dem i lampen på verandaen. - We buy two light bulbs and screw them into the lamp on the veranda.

Because we’re talking about a specific lamp and a specific veranda (the lamp on the veranda), but just two bulbs in general. In Norwegian, definiteness is usually marked with a suffix:

lampe → lampen (the lamp)
veranda → verandaen (the veranda)
lyspære → lyspærer is plural indefinite (two bulbs); the definite plural would be lyspærene (the bulbs).

What does dem refer to, and why is it dem and not something else?

Dem refers back to to lyspærer and is the object pronoun for plural “them.” Subject “they” is de. Singular objects would be den (for masculine/feminine nouns) or det (for neuter nouns).

Is it okay to write de instead of dem here?

Not in standard written Bokmål. Use de for subjects and dem for objects. In informal speech, many people say dem as a subject too, but avoid that in writing.

What does skru … i mean, and how does it differ from things like skru på/av/fast/inn?

skru i [noe]: screw something into something (physical action of turning with threads)
skru inn [noe] (i …): same idea as above, often adds a stronger sense of “into”
skru på [noe]: turn something on (e.g., skru på lyset = turn on the light)
skru av [noe]: turn something off
skru fast [noe] (i/på …): screw something firmly to/into something

Here, skru dem i lampen means “screw them into the lamp,” i.e., fit the bulbs into the lamp socket. Don’t use skru på here—that would mean “turn on.”

Can I say skru dem inn i lampen instead of skru dem i lampen?

Yes. Both are natural. Inn can emphasize the movement into the socket, but skru i is very common with light bulbs.

Where does the pronoun go with these verb + particle combinations?

With true particle verbs, the pronoun usually goes between the verb and the particle:

skru den på, slå det av. In our sentence, i lampen is a prepositional phrase (not a particle), but the same idea holds: place the object before the prepositional phrase: skrur dem i lampen, not “skrur i lampen dem.” If you add a particle like inn, it’s skru dem inn i lampen.

Why is it på verandaen and not i verandaen?

Use på for surfaces, platforms, and open areas (streets, islands, verandaer, etc.). Verandaen is a platform you’re “on,” so på verandaen. I is used for being “in” an enclosed space.

Does på verandaen tell me which lamp it is, or where the action happens?

As written, it most naturally modifies the nearest noun: the lamp. So it reads as “the lamp on the veranda.” If you want to say the action happens there, you can front the place phrase: På verandaen skrur vi dem i lampen.

Should there be a comma before og?

No. This is one clause with a compound predicate: “We buy … and screw …” Norwegian doesn’t use a comma before og in such cases. You’d add a comma only if you were linking two full independent clauses.

Do I need to repeat the subject vi after og?

No. One subject can govern both verbs: Vi kjøper … og skrur … Repeating vi is possible but unnecessary and stylistically odd here.

Can the present tense (kjøper, skrur) refer to future plans?

Yes. Norwegian often uses the present for near-future, especially in informal contexts or when the plan is clear. You can also say skal kjøpe … og skru … to make the intention explicit.

Why is lyspærer one word and not “lys pærer”?

Norwegian writes noun–noun compounds as a single word. Lys (light) + pærer (bulbs) → lyspærer. Hyphens are used only in special cases (e.g., to avoid ambiguity).

Can I write lampa instead of lampen? What about verandaen?

lampe is feminine, and Bokmål lets you choose either the common-gender forms (en lampe, lampen) or feminine forms (ei lampe, lampa). Both are acceptable; lampa is more colloquial.
veranda is typically written verandaen in the definite in Bokmål. You generally don’t use an -a definite form here in standard Bokmål.

Can I drop dem and just say: Vi kjøper to lyspærer og skrur i lampen?

No. Skru i needs a direct object here. Without dem, it’s incomplete. You could repeat the noun: … og skrur lyspærene i lampen, but using the pronoun dem is more natural and avoids repetition.

How do I pronounce the tricky bits like kjøper, lyspærer, skrur, verandaen?

kjøper: kj is a soft hiss (like German “ich”), ø like French “deux.” Roughly “SHØ-per.”
lyspærer: y is a rounded “ee,” æ like “a” in “cat.” Roughly “LEES-pæ-rehr.”
skrur: u is like a long “oo” with rounded lips; “skroor.”
verandaen: stress on the second syllable “-ran-”: “ve-RAN-da-en.”