hygiene vs hygienics

hygiene and hygienics both are nouns.

Word	Noun	Adjective	Verb	Adverb
hygiene	Yes	No	No	No
hygienics	Yes	No	No	No

As nouns, hygiene and hygienics are synonyms defined as:

hygiene and hygienics: the science concerned with the prevention of illness and maintenance of health

hygiene (noun)	hygienics (noun)
the science concerned with the prevention of illness and maintenance of health	the science concerned with the prevention of illness and maintenance of health
a condition promoting sanitary practices