Questions & Answers about Was ist gestern passiert?
Why do we use ist here instead of hat?
In German, the Perfekt (past) tense usually uses haben (to have) as a helper verb. However, verbs that describe movement, a change of state, or an event occurring, like passieren (to happen), use sein (to be) instead. Literally, this sentence translates to 'What is yesterday happened?'.
Why doesn't passiert start with ge- like most past tense verbs?
Normally, past participles get a ge- at the beginning, like gespielt or gemacht. But verbs that end in -ieren, like passieren, skip the ge- prefix. So it is just passiert, not gepassiert.
Why is passiert at the very end of the sentence?
This is the standard word order for the Perfekt tense. The helper verb (ist) takes the second position right after the question word (Was), and the main action verb (passiert) is pushed to the very end of the sentence.
Is Was the subject of this sentence?
Yes! Was (What) acts as the subject here. Because 'what' is treated as a singular thing, the helper verb must be conjugated in the third-person singular form, which is ist.