Learn Hardcore Serbian: Ne zaboravi da isključiš svetlo pre nego što odeš iz stana. - Do not forget to turn off the light before you leave the apartment.

Breakdown of Ne zaboravi da isključiš svetlo pre nego što odeš iz stana.

Why does the sentence start with Ne zaboravi? Is that an imperative?

Yes. Ne zaboravi is a negative imperative meaning don’t forget.

A few useful points:

In Serbian, this is a very common way to give a reminder or instruction.

Also, Serbian often uses the perfective verb in this kind of command when the speaker is talking about one complete action:

So here it sounds natural because the speaker is reminding someone about one specific action: turning off the light.

Why is it da isključiš instead of an infinitive like to turn off?

Because Serbian very often uses da + present tense where English uses an infinitive.

So:

zaboraviti da isključiš svetlo = literally to forget that you turn off the light
but naturally it means to forget to turn off the light

This pattern is extremely common in Serbian:

Although Serbian does have an infinitive, in everyday language da + present is often preferred.

What form is isključiš?