Conditions and Imperatives

The imperative in German is formed in two ways, depending on how polite you’re being.

The polite imperative is extremely simple: add Sie after the infinitive.

Bitte machen Sie das Licht aus.
Please turn off the light.

Setzen Sie sich hin.
Sit down.

To be honest, it’s not actually the infinitive. You’re cutting off the stem (turning machen into mach-) and then adding -en back on.

This produces the infinitive in all but one case: sein. Only with sein is it clear that you’re really adding something to the stem.

Seien Sie still!
Be quiet!

The familiar imperative (using du) takes the form of the standard conjugation without the -st.

If it takes an umlaut in its du conjugation, remove the umlaut:

Du fährst zu langsam. Fahr schneller!
You’re driving too slow. Drive faster!

There are three exceptions here: sein (becomes sei), wissen (becomes wisse), and werden (becomes werde). These last two are very rarely used.

Compared to that, the ihr form is a cinch: nothing changes at all from the normal form.

Bleibt hier.
Stay here.