What are the differences, perhaps in context, between the following expressions?
Was ist passiert?
Was ist geschehen?
Was ist aufgetreten?
German Language Stack Exchange is a bilingual question and answer site for speakers of all levels who want to share and increase their knowledge of the German language. It's 100% free, no registration required.Sign up to join this community
Regarding their overlap in sense, both words passieren and geschehen basically mean to happen. Another common translation is to occur.
I'd consider passieren slightly more colloquial, geschehen slightly more formal. According to the Wortschatz der Uni Leipzig passieren has a slight upper hand and, thus, is used more often.
Actually, it's quite hard to find an example where you cannot use both words but sometimes there's a tendency to one of them.
A couple of examples. In each example you can use both words. Though, I omitted the word which is less often in use for the specific example:
Was ist passiert/geschehen? (What happened?)
Lass es geschehen. (Let it pass/happen.)
Das darf nicht noch einmal passieren. (This must not happen again)
Die meisten Unfälle passieren in den eigenen vier Wänden. (Most accidents occur at home.)
Here a few sayings where I would use geschehen only:
Das geschieht dir recht. (It serves you right.)
... war es um jemanden geschehen (to be lost the moment)
nicht wissen wie einem geschieht (to not know what is happening)
As mentioned in comments there are a lot of words which share the meaning. Which words fit best depends on context. Vorfallen, ereignen and sich zutragen, for instance, can be used in context of an accident.
Der Unfall ist an dieser Stelle passiert/geschehen.
Der Unfall hat sich an dieser Stelle zugetragen/ereignet.
Was ist hier vorgefallen/passiert/geschehen?
Was hat sich hier zugetragen/ereignet?
The third word in question, however, is quite different. Auftreten can be translated as to occur as well but it's meaning is rather in the sense of to appear.
Welche Bands sind aufgetreten? (Which bands performed on page?)
... enorme Kräfte, die auftreten können. (... enormous forces that can occur.)
Schmerzen, die plötzlich auftreten. (Pain that appear suddenly.)
The question Was ist aufgetreten is not very idiomatic but might be found in a 'recipe' how to approach someone/something appropriately. For instance, if you'd ask a question on Stack Overflow about an error this particular question means something along 'What happened? Did you get a blue screen? Did your system freeze? What was the actual error message?'.
But other than this, there's no overlap.
Aside about the word passieren: In other context, it means to pass (in the sense of to move past), to negotiate, to traverse as in
to negotiate a steep rock face
and in cooking it means to pass through a sieve, e.g. passierte Tomaten, but you'll rarely encounter this verb usage if you're not a cook.