Re: what are the differences between psychedelics and hallucinogens?

In general, the term “hallucinogen” is applied a substance that causes the 
sensory perception (sight, sound, etc) of something that does not 
exist.  “Psychedelic” is a less technical term that refers to a substance 
that causes altered perceptions of one’s surroundings.  The difference 
between the two terms is not large, and you’ll probably find that most 
people will use them interchangeably.  The answer to your question may 
actually vary depending on who you ask.  Because of this, scientists 
prefer to use more precise and well-defined terms such as psychoactive and 
psychotropic, to name a few.