The usual requirements for describing events, as mandated by most journalism schools would be answering the following: "What," "where," "who," "why," and "how"?
It is the probability of that event.
Do you require an interpreter for your upcoming event?
The phrase commonly used to describe the event horizon in black holes is "point of no return."
The probability of an impossible event is 0 (zero).
went
A certainty.
There are a handful of adjective that could describe an event. They could be fun, exciting, joyful, breathtaking, elegant, whimsical, exhilarating, delightful, and wonderful.
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Four are enough to describe the moment of collision: three dimensions of space (WHERE) and one of time (WHEN). If you want anything more, such as the trajectories of the colliding objects before and after the event, you will require a set of 4 coordinates for each object or fragment.
Likelihood of event occurring.
likely
your mum has a bum