Source : Webster's Revised Unabridged Dictionary (1913)

Dis- \Dis-\ (?; 258)
   .

   1. A prefix from the Latin, whence F. d['e]s, or sometimes
      d['e]-, dis-. The Latin dis-appears as di-before b, d, g,
      l, m, n, r, v, becomes dif-before f, and either dis-or di-
      before j. It is from the same root as bis twice, and duo,
      E. two. See {Two}, and cf. {Bi-}, {Di-}, {Dia-}.
      Dis-denotes separation, a parting from, as in distribute,
      disconnect; hence it often has the force of a privative
      and negative, as in disarm, disoblige, disagree. Also
      intensive, as in dissever.

   Note: Walker's rule of pronouncing this prefix is, that the s
         ought always to be pronounced like z, when the next
         syllable is accented and begins with ``a flat mute [b,
         d, v, g, z], a liquid [l, m, n, r], or a vowel; as,
         disable, disease, disorder, disuse, disband, disdain,
         disgrace, disvalue, disjoin, dislike, dislodge, dismay,
         dismember, dismiss, dismount, disnatured, disrank,
         disrelish, disrobe.'' Dr. Webster's example in
         disapproving of Walker's rule and pronouncing dis-as
         diz in only one (disease) of the above words, is
         followed by recent ortho["e]pists. See {Disable},
         {Disgrace}, and the other words, beginning with dis-,
         in this Dictionary.

   2. A prefix from Gr. di`s- twice. See {Di-}.