tranquillize vs calm down

tranquillize and calm down both are verbs.

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

As verbs, tranquillize and calm down are synonyms defined as:

Other synonyms of tranquillize include calm, lull, quiet, quieten, still, tranquilize, tranquillise.

tranquillize (verb)	calm down (verb)
cause to be calm or quiet as by administering a sedative to	become quiet or less intensive
make calm or still	make calm or still
	become quiet or calm, especially after a state of agitation