regimen vs plan

regimen and plan both are nouns.

Word	Noun	Adjective	Verb	Adverb
regimen	Yes	No	No	No
plan	Yes	No	Yes	No

As nouns, plan is a hypernym of regimen; that is, plan is a word with a broader meaning than regimen:

Other hypernyms of regimen include program, programme.

regimen (noun)	plan (noun)
(medicine) a systematic plan for therapy (often including diet)	scale drawing of a structure
	a series of steps to be carried out or goals to be accomplished
	an arrangement scheme

regimen (verb)	plan (verb)
	make plans for something
	have the will and intention to carry out some action
	make or work out a plan for; devise