calm down vs placate

calm down and placate both are verbs.

Word	Noun	Adjective	Verb	Adverb
calm down	No	No	Yes	No
placate	No	No	Yes	No

As verbs, placate is a hyponym of calm down; that is, placate is a word with a more specific, narrower meaning than calm down:

Other hyponyms of calm down include lull, compose, appease, assuage, conciliate, gentle, gruntle, lenify, mollify, pacify.

calm down (verb)	placate (verb)
become quiet or less intensive	cause to be more favorably inclined; gain the good will of
make calm or still
become quiet or calm, especially after a state of agitation