The imperative

The imperative mood is one of the three verbal moods of the German language (the others being Indicative and Konjunktiv). It is used mainly to express commands, pieces of advice or invitations.

Weak verbs

The stem of the verb receives the following endings:

du:	-/-e	sag! sage!	rechne!
ihr:	-t/-et	sagt!	rechnet!
Sie:	-en Sie	sagen Sie!	rechnen Sie!

The 2nd person singular (du) imperative is formed from the Infinitive, by taking away the -n or -en of the ending. These forms are used without the pronoun du:

kaufe(n): Kaufe mir ein Buch!
rede(n): Rede nicht so laut!

Many verbs (all verbs in the case of the colloquial language), the whole -en ending can be removed:

kauf(en): Kauf mir ein Buch!
rauch(en): Rauch nicht so viel!
mach(en): Mach deine Aufgaben!

An exception to the rule above consists of all the verbs whose stem ends in -d, -t, -ig, or m/n preceded by a consonant(not l or r), can't remove the e.

antworte(n): Antworte mir sofort!
bade(n): Bade nicht so heiß!
entschuldige(n): Entschuldige bitte!

The second person plural form of the imperative corresponds to the present form, without the ihr:

hören: Hört auf eure Eltern!
öffnen: Öffnet die Tür!

The polite second-person form corresponds to the present form (has both plural and singular meaning). The only change is that the personal pronoun Sie stays after the verbs:

kaufen: Kaufen Sie das Buch!
öffnen: Öffnen Sie bitte die Tür!

Weak verbs

The imperative of strong verbs has the following forms:

du:	-/-e	komm! komme!	nimm!	biete!
ihr:	-t/-et	kommt!	nehmt!	bietet!
Sie:	-en Sie	kommen Sie!	nehmen Sie!	bieten Sie!

Strong verbs are conjugated almost exactly like weak verbs, except the case in which a verb changes its stem vowel to i in the second-person present form(nimmst, hilfst). In this case, the ending of the conjugation is lost.