Here are some other terms that might be used, depending on the specific context:

* Phenomenon: A natural event or occurrence.

* Fact: A statement that is demonstrably true.

* Observation: A statement based on direct sensory experience or measurement.

* Data: Information gathered through observation or experimentation.

* Hypothesis: A proposed explanation for an observation.

* Theory: A well-substantiated explanation of some aspect of the natural world.

The best term to use depends on the specific context and the level of certainty or explanation being offered.