Phænomenon

Phænomenon is an historical variant spelling of the English noun phenomenon. It uses the ligature æ (æ) that was common in Early Modern English typography. The term ultimately derives from the Greek phainomenon, from phaínesthai "to appear." In English, a phenomenon is a fact, occurrence, or event that can be observed, and it is often something noteworthy or unusual.

The standard modern spelling is "phenomenon" in the singular and "phenomena" in the plural, borrowed from the same Greek root. The spelling phænomenon was common in earlier centuries and appears in older texts; in some editions the plural is written as phænomena. The anglicized plural "phenomenons" exists but is rare and generally considered nonstandard.

Today phænomenon is largely regarded as archaic and is encountered mainly in historical works, typographic reprints, or stylistic uses to evoke a past period. In scientific and academic writing, editors replace it with the standard "phenomenon" or "phenomena" to conform with contemporary orthography. The term also occurs in philosophy related to Kant's distinction between phenomena (appearances) and noumena (things-in-themselves).