gentle vs tranquillize

gentle is an adjective but tranquillize is not an adjective.

Word	Noun	Adjective	Verb	Adverb
gentle	No	Yes	Yes	No
tranquillize	No	No	Yes	No

As verbs, tranquillize is a hypernym of gentle; that is, tranquillize is a word with a broader meaning than gentle:

Other hypernyms of gentle include calm, calm down, lull, quiet, quieten, still, tranquilize, tranquillise.

gentle (adjective)	tranquillize (adjective)
marked by moderate steepness
having little impact
soft and mild; not harsh or stern or severe
belonging to or characteristic of the nobility or aristocracy
quiet and soothing
easily handled or managed
having or showing a kindly or tender nature

gentle (verb)	tranquillize (verb)
stroke soothingly	cause to be calm or quiet as by administering a sedative to
cause to be more favorably inclined; gain the good will of	make calm or still
give a title to someone; make someone a member of the nobility