General:
* Event: This is a broad term that encompasses any occurrence, big or small.
* Occurrence: Similar to event, but perhaps emphasizing the fact that it happened.
* Happenstance: This term implies that the event is unplanned or accidental.
Specific:
* Incident: This term often suggests a significant or noteworthy event, especially one that may be negative or disruptive.
* Action: This implies a deliberate act or a change in state.
* Phenomenon: This term is used for something unusual or noteworthy, often referring to a natural event.
Others:
* Activity: This term implies a dynamic process.
* Situation: This term refers to a set of circumstances or conditions.
Ultimately, the best term depends on the specific meaning you want to convey. For example, if you're talking about a surprising event, "happenstance" might be appropriate. If you're talking about a significant event that happened, "incident" could be a better fit.