The Collaborative International Dictionary of English v.0.48:

Hygiene \Hy"gi*ene\, n. [F. hygi[`e]ne. See Hygeia.]
   That department of sanitary science which treats of the
   preservation of health, esp. of households and communities; a
   system of principles or rules designated for the promotion of
   health.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Regimen \Reg"i*men\ (r?j"?*m?n), n. [L. regimen, -inis, fr.
   regere to guide, to rule. See Right, and cf. Regal,
   R['e]gime, Regiment.]
   1. Orderly government; system of order; adminisration.
      --Hallam.
      [1913 Webster]

   2. Any regulation or remedy which is intended to produce
      beneficial effects by gradual operation; esp. (Med.), a
      systematic course of diet, etc., pursed with a view to
      improving or preserving the health, or for the purpose of
      attaining some particular effect, as a reduction of flesh;
      -- sometimes used synonymously with hygiene.
      [1913 Webster]

   3. (Gram.)
      (a) A syntactical relation between words, as when one
          depends on another and is regulated by it in respect
          to case or mood; government.
      (b) The word or words governed.
          [1913 Webster]

WordNet (r) 3.0 (2006):

hygiene
    n 1: a condition promoting sanitary practices; "personal
         hygiene"
    2: the science concerned with the prevention of illness and
       maintenance of health [syn: hygiene, hygienics]

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "hygiene":
   antisepsis, decontamination, disinfection, disinfestation,
   epidemiology, flash pasteurization, fumigation, health physics,
   hygenics, hygienics, mental hygiene, pasteurization,
   preventive dentistry, preventive medicine, prophylactic psychology,
   prophylactodontia, prophylaxis, public health, sanitation,
   sterilization