Etymology

Etymology is the study of the history of the form of words, the origin, and evolution of their meaning across time.

The word etymology derives from the Greek word “etumología” which can be split up in itself as “étumon” meaning “true sense or sense of a truth”, and “logia” meaning “the study of”.

Psychedelics

Psychedelics, also known as hallucinogens, entheogens, or empathogens, are psychoactive substances that induce changes in the nervous system and result in alterations in conscious experience. These can include changes in cognition, perception, feelings, and emotions.

The term “psychedelic” was invented by psychiatrist Humphrey Osmond in 1957.

It is derived from the Greek word “psychḗ” which means “soul, mind” and “dēleín”, “to manifest”, with the intended meaning “mind manifesting” or “soul manifesting”, the implication being that psychedelics can reveal unused potentials of the human mind.

Over the years many different names have been proposed to define this specific drug class. The most popular names, hallucinogen, entheogens, and psychedelic have often been used interchangeably.

Hallucinogen

The word hallucinogen is derived from the word “hallucination”. The term hallucinate dates back to around 1595–1605, and is derived from the Latin “hallūcinātus”, the past participle of “(h)allūcināri”, meaning “to wander in the mind”.

Most hallucinogens can be categorized as either psychedelics, dissociatives, or deliriants.

Entheogen

The term is derived from two words in Ancient Greek, “éntheos” and “genésthai”. The adjective entheos translates to English as “full of the god, inspired, possessed”, and is the root of the English word “enthusiasm”. The Greeks used it as a term of praise for poets and other artists. Genesthai means “to come into being”.

Thus, an entheogen is a drug that causes one to become inspired or to experience feelings of inspiration, often in a religious or “spiritual” manner.

Emphatogen

The term empathogen, meaning “generating a state of empathy”, was coined in 1983–84 by Ralph Metzner as a term to denote a therapeutic class of drugs that includes MDMA and phenethylamine relatives. David E. Nichols later rejected this initial terminology and adopted, instead, the term entactogen, meaning “producing a touching within”, to denote this class of drugs, asserting a concern with the potential for an improper association of the term empathogen with negative connotations related to the Greek word “páthos” meaning “suffering, passion”.

Empathogens or entactogens are a class of psychoactive drugs that produce experiences of emotional communion, oneness, relatedness, and emotional openness, that is, empathy or sympathy.

Summary

Because of the complexity of these substances, it is hard to be specific about how a certain compound is going to act physiologically, and psychologically. Therefore a clear definition is still open for discussion. But despite the various usage of words describing similarities, there seems to be an overall consensus that all describe psychoactivity.