This is the 318th most frequent German word.
unfall
Accident
Here, 'Unfall' is used to describe a physical accident or collision.
Der Unfall auf der Autobahn führte zu einem Stau.
The accident on the highway caused a traffic jam.
In this sentence, 'Unfall' is metaphorically used to imply a coincidence or unplanned event.
Es war ein Unfall, dass wir uns dort getroffen haben.
It was an accident that we met there.
Here, 'Unfälle' is used in a general sense to describe minor incidents or mishaps.