Phenomena are occurrences or strange happenings that typically cannot be explained by science, for example ball lightning or the efficacy of prayer. In scientific circles, the word carries a bit of a negative connotation.
The word comes from the Greek phainomenon, the active participial form of a verb meaning "appear".
Examples of so-far-unexplained phenomena include:
On the other hand, when scientists believe they have truly explained some process, such as evolution or the Big Bang, they are rarely called phenomena anymore.