Phenomenon has a specialized meaning in the philosophy of Immanuel Kant who opposed the term 'Phenomenon' to 'Noumenon'. Phenomena constitute the world as we experience it, as opposed to the world as it exists independently of our experiences (thing-in-themselves). Humans cannot, according to Kant, know things-in-themselves, only things as we experience them. Thus philosophy should concern itself with understanding the process of experience itself.
Kant's account of phenomena has also been understood as influential in the development of psychodynamic models of Psychology, and of theories concerning the ways in which the brain, mind and external world interact.
It is possible to list the phenomena which are relevant to almost any field of endeavor, for example, in the case of optics and light one can list observable phenomena under the topic optical phenomenon.
The possibilities are many, for example:
Biological phenomenon biology Chemical phenomenon chemistry Electrical phenomenon electricity Geological phenomenon geology Meteorological phenomenon weather Optical phenomenon optics Physical phenomenon physics Statistical phenomena statistics Thermal phenomenon thermodynamics
Some observable events are commonplace, some require delicate manipulation of expensive and sensitive equipment. Some are significant experiments which led to groundbreaking discoveries.
There is a class of phenomena which lie outside generally accepted knowledge which knowledgeable scientists tend to discount. They are collected and discussed under the topic anomalous phenomenon