Source : Webster's Revised Unabridged Dictionary (1913)

Mal- \Mal-\
   A prefix in composition denoting ill,or evil, F. male, adv.,
   fr. malus, bad, ill. In some words it has the form male-, as
   in malediction, malevolent. See {Malice}.

   Note: The formmale- is chiefly used in cases where the c,
         either alone or with other letters, is pronounced as a
         separate syllable, as in malediction, malefactor,
         maleficent, etc. Where this is not the case, as in
         malfeasance or male-feasance, malformation or
         male-formation, etc., as also where the word to which
         it is prefixed commences with a vowel, as in
         maladministration, etc., the form malis to be
         preferred, and is the one commonly employed.