German: Formal or Informal Greetings
German speakers generally place great value on showing respect toward each other and strangers. The language itself allows the speaker to make a clear distinction between formal and informal ways of saying you. (Once upon a time, English did this, too, but English speakers dropped the thee and thou forms long ago.)
In German, you use either the formal Sie (zee) (you) or one of the two informal forms: du (dooh) (you), if you’re talking to one person, or ihr (eer) (you, you guys, you all), if you’re addressing two or more people.
Making the distinction between the informal and formal you forms is important. Why? Because people are likely to consider you impolite and disrespectful if you use the informal way of addressing them in a situation that calls for more formality.
In general, you use the formal Sie for everyday communication with people outside your circle of family and friends. Even among people who are in regular contact with one another (neighbors or coworkers, for example), Sie is often used as a means of showing respect. As you get to know somebody better, you may switch to du.
However, no hard and fast rules apply when it comes to using du or Sie. In fact, many exceptions exist. For example, suppose a German friend takes you to a party. Even though you and the other guests are complete strangers, the other guests may just address you with du — especially if they’re easygoing — so you may address them with du as well.
If you’re the least bit unsure of whether to use du or Sie, use Sie until the person you’re addressing asks you to use du or addresses you with du.