Danish has two distinct words both spelled at, and Danes themselves regularly misspell one of them. The first is the infinitive marker at ("to"), as in at sove ("to sleep"). The second is the complementiser at ("that"), as in Jeg ved, at du sover ("I know that you are sleeping"). They look identical on the page but are different words with different jobs, different pronunciations, and different rules. This page gives you a one-line test to tell them apart, and then tackles the notorious og/at spelling trap that flows from the way they sound.
The one-line decision test
Look at what follows the word.
- If an infinitive verb follows (the bare (at)
- verb form), it is the infinitive marker at = "to."
- If a finite clause follows — a clause with its own subject and a tensed verb — it is the complementiser at = "that."
| Infinitive at ("to") | Complementiser at ("that") | |
|---|---|---|
| What follows | an infinitive verb | a full clause (subject + finite verb) |
| English | to | that |
| Pronunciation | [ɑ] — like og | [æd] — the -t is heard |
| Can be dropped? | No | Yes |
| Example | Jeg prøver at sove. | Jeg ved, at du sover. |
Jeg prøver at sove.
I'm trying to sleep. (infinitive at — followed by the infinitive 'sove')
Jeg ved, at du sover.
I know that you are sleeping. (complementiser at — followed by the clause 'du sover')
The infinitive at: "to"
The infinitive marker introduces an infinitive verb, exactly the way English "to" introduces the base form. It appears after many verbs (prøve, forsøge, beslutte, glemme, lære), after adjectives (svært at forstå), and as the citation form of any verb in a dictionary (at gå, at være).
Det er svært at forstå hans accent.
It's hard to understand his accent.
Hun har besluttet at flytte til Aarhus.
She has decided to move to Aarhus.
Jeg glemte at låse døren.
I forgot to lock the door.
Crucially, this at cannot be deleted. Jeg prøver sove is ungrammatical, just as English "I try sleep" is wrong. The infinitive marker is structurally required.
The complementiser at: "that"
The complementiser introduces an entire embedded clause — a statement reported as the content of knowing, saying, believing, or hoping. It corresponds to English "that," and like English "that," it is frequently optional in everyday speech and writing.
Jeg håber, at du har det godt.
I hope (that) you're doing well.
Hun sagde, at hun kom for sent.
She said (that) she'd be late.
Vi tror, at det bliver regn.
We think (that) it's going to rain.
You can drop it without changing the meaning:
Jeg håber, du har det godt.
I hope you're doing well. (complementiser at dropped — still fully correct)
This drop-vs-no-drop behaviour is itself a reliable test: if the at can vanish and the sentence survives, it's the complementiser. Try deleting the at in Jeg prøver at sove and the sentence collapses — proof it's the infinitive marker.
The og / at trap: why even Danes get it wrong
Here is the heart of the difficulty. The infinitive marker at is pronounced [ɑ] — identical to the conjunction og ("and"), which is also pronounced [ɔ]/[ɑ] with a silent -g. In normal speech, at sove and og sove sound the same. Because of this, a huge proportion of Danish writers — native speakers included — mix up og and at in writing. It is the single most stigmatised spelling error in Danish.
The rule that disentangles them:
- Infinitive after a verb → at (the infinitive marker).
- Two finite verbs joined as equals → og (the conjunction).
❌ Jeg prøver og sove.
Incorrect — the classic og/at error; 'sove' is an infinitive, so it needs the infinitive marker 'at'.
✅ Jeg prøver at sove.
I'm trying to sleep.
Compare a genuine og case, where two finite verbs are coordinated:
Jeg står op og laver kaffe.
I get up and make coffee. (two finite verbs — 'står' and 'laver' — joined by 'og')
The test natives are taught in school: replace the suspected word with 'to' (at) vs 'and' (og) in your head, or swap the verb into a different tense. If the second verb can change tense alongside the first (Jeg stod op *og lavede kaffe), it's coordinated — use *og. If the second verb stays an infinitive no matter what (Jeg prøvede *at sove), it's the infinitive marker — use *at.
Jeg stod op og lavede kaffe.
I got up and made coffee. (both verbs went to past tense — confirms 'og')
Jeg prøvede at sove.
I tried to sleep. ('sove' stays infinitive — confirms 'at')
A note for English speakers: don't confuse at with og at all
English keeps "to" (infinitive), "that" (complementiser), and "and" (conjunction) as three visibly different words, so you rarely confuse them. Danish merges the sounds of two of them (at infinitive ≈ og) while keeping the spelling of at shared across two functions. So your two jobs are opposite to a Dane's: a Dane must learn to spell the sound apart; you, coming from English, must learn that one written word at does two grammatical jobs, and that it is not the same word as og even though it sounds like it.
Common Mistakes
❌ Jeg har lyst til og rejse.
Incorrect — 'rejse' is an infinitive, so it must be the infinitive marker 'at', not 'og'.
✅ Jeg har lyst til at rejse.
I feel like travelling.
❌ Det er vigtigt og du kommer til tiden.
Incorrect — a full clause ('du kommer...') follows, so it needs the complementiser 'at'.
✅ Det er vigtigt, at du kommer til tiden.
It's important that you arrive on time.
❌ Hun begyndte og græde.
Incorrect — 'græde' is an infinitive; use the infinitive marker 'at'.
✅ Hun begyndte at græde.
She started to cry.
❌ Jeg synes at og hun har ret.
Incorrect — doubling 'at og'; only the single complementiser 'at' belongs here.
✅ Jeg synes, at hun har ret.
I think that she's right.
❌ Han lovede at og hjælpe os.
Incorrect — same doubling error before an infinitive; use a single 'at'.
✅ Han lovede at hjælpe os.
He promised to help us.
Key Takeaways
- One spelling, two words: infinitive at ("to") and complementiser at ("that").
- Decision test: infinitive verb follows → "to"; full clause (subject + tensed verb) follows → "that."
- The complementiser at is droppable; the infinitive at is not — that's your quickest check.
- The infinitive at sounds like og, which is why even natives miswrite it. Coordinated finite verbs take og; an infinitive after a verb takes at.
- The tense-swap test settles og vs at: if both verbs can change tense together, it's og; if the second stays infinitive, it's at.
Now practice Danish
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Start learning Danish→Related Topics
- Som, Der and At as ConnectorsB2 — A disambiguation guide to Danish's overlapping little connectors — relative vs comparative som, relative vs expletive der, and the complementiser at vs the infinitive marker at.
- Uses of the InfinitiveB1 — Where the bare infinitive and the at-infinitive appear in Danish — after modals, after other verbs and prepositions, as subject or object, in for at / uden at / ved at, and as instructions on signs.
- Reported Speech and BackshiftB2 — How Danish turns direct quotes into indirect speech — the complementiser at, tense backshift, pronoun and deictic shifts, reported questions with om and hv-words, and modal backshift.