The imperative

When you tell somebody to do something — turn left, wait here, call me — Serbian does not use the ordinary present tense. It uses a separate command form, and you already have everything you need to build it: it comes off the present tense you learned in lessons twelve to fourteen.

Where the command form comes from

Take the they form of the present — gledaju, govore, pišu, idu — cut off its ending, and what is left is the command stem. Add -j or -i to it and you are telling one person what to do.

• a-verbs: gledaju → gleda- → gledaj! (look!)
• i-verbs: govore → govor- → govori! (speak!)
• e-verbs: pišu → piš- → piši! (write!)

For more than one person, or for one person you address politely, add -te. For let's do it together, add -mo. The three endings sit on the same stem, so once you have the singular you have all three.

Do not try to build the command form off the infinitive. pisati would give you nothing usable; pišu gives you piši. The they form is the one to look at, every time.

A few more you will use every day, singular beside plural: reci → recite (say, tell), sedi → sedite (sit down), pređi → pređite (cross), sačekaj → sačekajte (wait a moment), skreni → skrenite (turn).

The -te form is also the polite form

This matters more day to day than the paradigm does. Serbian addresses a stranger, an older person or anyone you are being formal with as vi — and the command form that goes with vi is the same -te form you use for a group. So Skrenite levo is both turn left said to several people and turn left said politely to one.

• To a friend: Skreni levo. — Turn left.
• To a stranger, or to a group: Skrenite levo. — Turn left.
• Stopping someone in the street: Sačekajte me, molim vas. — Wait for me, please.
• In someone's office: Sedite, molim vas. — Have a seat, please.

When in doubt in the street, in a shop or at a counter, use the -te form. Using it with a friend sounds a little stiff; using the bare singular with a stranger sounds rude, and that is the more expensive mistake.

Let's: the -mo form

The -mo form means let's: Idimo! (let's go), Pređimo most. (let's cross the bridge), Sačekajmo malo. (let's wait a bit). In everyday speech people very often just use the ordinary present we form for this — Idemo! is what you will actually hear most — but the -mo command is the form that belongs to this set, and it is always correct.

Telling someone NOT to do something

Here Serbian does something you have to learn as a fixed pattern: it does not put ne in front of the command form. Instead it uses a helper word, nemoj to one person and nemojte to several or politely, followed by the infinitive.

Both completions work, exactly as with the modal verbs in the last lesson: nemoj takes either the infinitive or da plus the present. Nemoj zaboraviti and Nemoj da zaboraviš are the same sentence, and the da version is if anything the commoner one in speech. So: Nemojte žuriti. (don't hurry), Nemoj da se izgubiš. (don't get lost).

nemoj / nemojte changes for the person you are talking to and nothing else. The verb after it never becomes a command form: Nemojte čekati, never Nemojte čekajte.

You will still meet ne in front of a command in a handful of fixed expressions — Ne brini! (don't worry), Ne žuri! (no rush) — but you do not need to produce those. Build your own negative commands with nemoj and nemojte and you will always be right.