The terms empathogen and entactogen are different terms used to describe a class of psychoactive drugs that produce distinctive emotional and social effects similar to those of MDMA ("ecstasy").
The term "empathogen" was coined in 1983 by Ralph Metzner to denote chemical agents inducing feelings of empathy.
"Entactogen" was coined by David E. Nichols as an alternative to "empathogen", attempting to avoid the potential for improper association of the latter with negative connotations related to the Greek root "pathos" (suffering).
The word "entactogen" is derived from the roots "en" (Greek: within), "tactus" (Latin: touch) and "gen" (Greek: produce) (Nichols 1986: 308).
Neither term is dominant in usage, and, despite their difference in connotation, are essentially interchangeable, as they refer to precisely the same chemicals.