active placebo vs placebo

active placebo and placebo both are nouns.

Word	Noun	Adjective	Verb	Adverb
active placebo	Yes	No	No	No
placebo	Yes	No	No	No

As nouns, placebo is a hypernym of active placebo; that is, placebo is a word with a broader meaning than active placebo:

active placebo: a placebo used in experimental tests of a drug that has noticeable side effects
placebo: an innocuous or inert medication; given as a pacifier or to the control group in experiments on the efficacy of a drug

active placebo (noun)	placebo (noun)
a placebo used in experimental tests of a drug that has noticeable side effects	(Roman Catholic Church) vespers of the office for the dead
	an innocuous or inert medication; given as a pacifier or to the control group in experiments on the efficacy of a drug