Causal clauses (då)

You may already know as "then" or "when". In formal or written Swedish, it is also a subordinating conjunction meaning "since" or "because".

Using "då" for Causality

Like eftersom (because), connects a subordinate clause to a main clause to explain a cause.

since, because
The visibility was bad because the fog came in.
Sikten var dålig då dimman kom in.
The lighthouse keeper thrived, since the isolation gave him peace and quiet.
Fyrvaktaren trivdes bra, då isoleringen gav honom lugn och ro.

Starting with "då" (The V2 Rule)

You can place the -clause at the beginning of your sentence. Because Swedish strictly uses V2 (verb-second) word order, the entire subordinate clause acts as the first element. This means the main clause immediately following the comma must start with a verb.

Since the lighthouse is old, the glow is weak.
Då fyren är gammal, är skenet svagt.
Since the visibility is zero in the fog, most seafarers stay at home.
Då sikten är noll i dimman, stannar de flesta sjöfarare hemma.

Adverbs in Subordinate Clauses

Since introduces a subordinate clause, sentence adverbs like plötsligt (suddenly) or nyligen (recently) are placed before the first verb in the clause.

The lighthouse keeper looks out because the visibility suddenly gets bad.
Fyrvaktaren tittar ut då sikten plötsligt blir dålig.
The glow probably won't go out, since they have recently renovated the remote lighthouse.
Skenet lär inte slockna, då man nyligen har renoverat den avlägsna fyren.