The imperative (imperativ) is the command form of a verb — used for orders, instructions, requests, and warnings ("Sit!", "Wait!", "Open the door!"). It's normally the shortest form of the verb.

The rule: take the present tense and remove the final -r.

Presens − r = Imperativ

The trick — does it keep the final -a or not? Almost every Swedish verb's infinitive ends in -a, so it's tempting to assume the imperative does too. It doesn't always — it depends on the present tense ending, not the infinitive:

• Present tense ends in -ar (verb group 1, e.g. prata → pratar): the imperative keeps the -a. pratar − r = prata → "Prata!"
• Present tense ends in -er (verb group 2, and most irregular/strong verbs, e.g. läsa → läser): the imperative loses the -a completely. läser − r = läs → "Läs!"

So prata and läsa both end in -a in the infinitive, but their imperatives come out completely different shapes — "Prata!" keeps it, "Läs!" drops it. You have to know the present tense, not just the infinitive, to know which one you get.

Negative commands: put inte right after the imperative — Prata inte i telefonen! (Don't talk on the phone!), Stäng inte dörren! (Don't close the door!).

Vara (to be) doesn't follow the present-tense-minus-r rule at all — its present tense is the irregular är, but its imperative is Var! (as in "Var snäll!" — "Be kind!"). A handful of very common verbs are irregular like this; everything else follows the -ar/-er rule above.