"Call me in case of emergency."

Translation: Ring mig i nödfall.

[deactivated user]

Why is it that when giving some commands with verbs, the a ending is used, but in some cases like this, it's not?

[Berniebud]

There's a bit of a trick to it, when the present tense of the verb ends in "-ar", the "Command" form ends in "-a".

If the present tense ends in "-er", then the "-a" is completely removed.

"Kollar" -> "Kolla!" -> "Look!"

"Tänker" -> "Tänk!" -> "Think!"