regime vs regimen

regime and regimen both are nouns.

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

As nouns, regime and regimen are synonyms defined as:

regime and regimen: (medicine) a systematic plan for therapy (often including diet)

regime (noun)	regimen (noun)
(medicine) a systematic plan for therapy (often including diet)	(medicine) a systematic plan for therapy (often including diet)
the organization that is the governing authority of a political unit