Documented in the Late Latin phaenomĕnon, referring to the Greek phainomenon, for describing a thought by an individual that is reflected in reality as an experience that escapes the commonplace, even alluding to something that appears to be real, associated with the passive verb phainesthai, for ‘appeared’, from the verb phainein, for ‘to show’ or ‘to appear’, with roots in the Indo-European *bha(1), interpreted as ‘to shine’ or ‘ to illuminate’.

The core defined by *bha-(1) extends to words such as photograph (conjugating the Greek elements phôs and gráphein), fantasy (given in Greek as phantasia), or fable (from the Latin fabŭla).
A phenomenon responds to something with extraordinary characteristics manifested in a certain time and space, which can have a positive or negative effect depending on the circumstances. A natural disaster as well as the appearance of a rainbow can be classified using this term.