Phenomena is the plural of phenomenon, which most generally refers to an observable occurrence or circumstance.

By far the most common and universally accepted plural form is the classical phenomena; the Anglicised phenomenons is also sometimes used. The plural form phenomena is frequently used in the singular, and the singular form is sometimes used in the plural.

A phenomenon, which is defined as a “a fact directly observed, a thing that appears or is perceived, an occurrence,” originally came from the Greek word, phainomenon “that which appears or is seen.” Most dictionaries list phenomena as the plural of phenomenon, some include phenomenons, though notably this is the Americanized/modern plural form.