A phenomenon is an observable event or occurrence, often used to describe something unusual or notable. Learn how the term is used in philosophy, science, sociology and other fields, and see some examples of phenomena. PHENOMENA definition: 1. plural of phenomenon 2. plural of phenomenon. Learn more. That's right, the difference between phenomenon vs. phenomena is simply the number of experiences you may be referring to. Learn more about this here! Learn the meaning of phenomenon, a word that describes something unusual or difficult to explain, or someone or something very impressive or popular. See examples of natural phenomena, literary phenomena, and cultural phenomena.