Regimen vs Regimes - What's the difference?

As a noun regimen

is .

(en-noun)

Orderly government; system of order; administration.

Any regulation or remedy which is intended to produce beneficial effects by gradual operation.

* 1832 , The Edinburgh Review (page 470)

Seven or eight annual bloodings, and as many purgations — such was the common regimen the theory prescribed to ensure continuance of health

(grammar) A syntactical relation between words, as when one depends on another and is regulated by it in respect to case or mood; government.