The plural of "phenomenon" is "phenomena." The phenomena of light refraction and reflection are still being studied. The phenomena observed in this study were significant. The noun "phenomenon" has a Greek root, which is the derivation of the plural "phenomena."

The plural of phenomenon is phenomena. The adjective phenomenal is most commonly used to mean highly extraordinary or exceptional, as in It was a phenomenal display of skill. It can also be used more generally to mean relating to phenomena in some way, as in My philosophy paper deals with the phenomenal qualities of existence.