Passive
There are two kinds of passive in Swedish, the s-passive and the perifrastic passive. Their forms are easy to learn, the problem is to know when to use the passive.
Perifrastic passive
The perifrastic passive is formed with an auxiliary verb, bli (become) or vara (be), plus a perfect participle. The participle is inflected as an adjective, as usual:
Swedish English
Huset var redan byggt. The house was already built.
Husen var redan byggda. The houses were already built.
Kyrkan var redan byggd. The church was already built.
Agent
If there is an agent in a passive sentence – the agent is the one who performs the action of the verb – the preposition av is used:
Huset byggdes av tre bröder. ~ The house was built by three brothers.