Few Danish phrasal verbs trip up English speakers as quickly as lukke op. The trap is that the base verb lukke on its own means close, not open — yet add the little particle op and the whole thing flips to mean open (or open up). This page shows you the full pattern, the particle logic that powers it, and how to keep lukke op apart from its near-synonym åbne.
Principal parts
Lukke op is built on the weak -ede verb lukke. The particle op does not conjugate — only the verb does.
| Form | Danish | English |
|---|---|---|
| Infinitive | (at) lukke op | to open / open up |
| Present | lukker op | open(s) up |
| Past | lukkede op | opened up |
| Past participle | lukket op | opened up |
| Imperative | Luk op! | Open up! |
The particle flips the meaning
The verb lukke describes operating a closable opening — a door, a window, a lid, your eyes. By itself it defaults to closing it. The direction of the action is then set by the particle:
- lukke i — close (shut it)
- lukke op — open (open it up)
So the same verb spans both directions, and the particle tells you which way the door is moving. English does something similar with open up versus shut, but it does not use one verb for both — which is exactly why learners expect lukke to mean open. It does not.
Kan du lukke døren op? Det er for varmt herinde.
Can you open the door? It's too warm in here.
Luk vinduet i — det blæser ind.
Close the window — it's blowing in.
Hun lukkede op for vandet og fyldte glasset.
She turned on the water and filled the glass.
Notice that with a direct object, the particle often jumps to the end of the clause: lukke døren op, not lukke op døren. With no object stated, the verb and particle sit together: Luk op!
Present tense
In the present, lukker op covers both open up right now and as a habit.
Jeg lukker op, hvis det er postbuddet.
I'll open the door if it's the mail carrier.
Butikken lukker op klokken ti om søndagen.
The shop opens at ten on Sundays.
Past tense
The past is lukkede op, with the regular -ede ending on lukke.
Da jeg lukkede op, stod der ingen udenfor.
When I opened the door, there was nobody standing outside.
De lukkede op for gæsterne lidt før tid.
They opened up for the guests a little ahead of time.
Present perfect
The perfect uses har as its auxiliary, plus the participle lukket op.
Har du lukket op for varmen? Der er blevet rigtig hyggeligt.
Have you turned the heating on? It's gotten really cozy.
Vi har lige lukket op, så der er stadig ikke mange kunder.
We've just opened, so there still aren't many customers.
Common collocations
These fixed combinations are worth memorizing as units:
- lukke op for
- noun — turn on / open up (the water, the heating, the radio): lukke op for radioen
- lukke døren op — open the door
- lukke op (for nogen) — answer the door, let someone in
- Luk op! — Open up! (a knock-at-the-door imperative)
- lukke øjnene op — open one's eyes (also figuratively, be enlightened)
Luk lige op for radioen — der er nyheder nu.
Turn the radio on, would you — the news is on now.
Lukke op vs. åbne
Danish also has the plain verb åbne, which is the more neutral, often more formal word for open. Both can open a door, but they are not interchangeable everywhere:
- åbne is used for things you unseal or inaugurate: a bottle, a letter, a bank account, a shop as an institution (butikken åbner), an exhibition.
- lukke op is the everyday, physical open it up — especially answering a door or turning on a tap.
You would say åbne en flaske vin (open a bottle of wine), not lukke en flaske op; but at the front door you would naturally say Jeg lukker op rather than Jeg åbner. See åbne for the full picture, and lukke for the close side of the pair.
Vil du åbne vinen, mens jeg lukker op for gæsterne?
Will you open the wine while I let the guests in?
Mini-dialogue
— Der bliver banket på. Luk lige op! — Jeg kan ikke — jeg står med hænderne fulde. Kan du ikke selv lukke op? — Fint, jeg lukker op.
— Someone's knocking. Get the door, would you! — I can't — my hands are full. Can't you answer it yourself? — Fine, I'll get it.
Common mistakes
❌ Kan du lukke døren? Jeg vil gerne have luft.
Incorrect — luk(ke) døren means CLOSE the door, the opposite of what's intended.
✅ Kan du lukke døren op? Jeg vil gerne have luft.
Correct — lukke ... op means open the door.
❌ Jeg lukker, da det banker på.
Incorrect — lukke alone says you're shutting something when you mean to answer the door.
✅ Jeg lukker op, da det banker på.
Correct — lukke op is the verb for answering / opening the door.
❌ Lukke op flasken, tak.
Incorrect — for unsealing a bottle Danish uses åbne, and the particle is misplaced.
✅ Åbn flasken, tak.
Correct — use åbne for opening a bottle.
❌ Hun lukkede op døren langsomt.
Incorrect — with a stated object the particle op goes after it.
✅ Hun lukkede døren op langsomt.
Correct — lukkede døren op, particle after the object.
Key takeaways
- lukke alone = close; the particle op flips it to open, and i makes the close direction explicit.
- Conjugate only the verb: lukker op / lukkede op / har lukket op; the particle op is fixed.
- With an object, the particle follows it: lukke døren op.
- Reach for åbne when you unseal or inaugurate something; reach for lukke op for the physical, everyday open it / answer the door.
Now practice Danish
Reading grammar gets you part of the way. The exercises are where it sticks — free, no signup needed.
Start learning Danish→Related Topics
- LukkeA1 — Full reference for lukke ('to close / shut') — principal parts, the regular -ede pattern across all core tenses, and the particle pair that flips its meaning: lukke op = open, lukke i = close.
- ÅbneA1 — Full reference for åbne ('to open') — principal parts, the regular -ede pattern across all core tenses, its starring role in the passive (døren åbnes / døren bliver åbnet), and the -s vs blive passive choice.
- The ImperativeA1 — How to give commands, requests and suggestions in Danish — the bare-stem imperative, polite softeners, and the idiomatic 'don't' with lad være med at.