Source : Webster's Revised Unabridged Dictionary (1913)

Per- \Per-\ [See {Per}.]
   1. A prefix used to signify through, throughout, by, for, or
      as an intensive as perhaps, by hap or chance; perennial,
      that lasts throughout the year; perforce, through or by
      force; perfoliate, perforate; perspicuous, evident
      throughout or very evident; perplex, literally, to
      entangle very much.

   2. (Chem.) Originally, denoting that the element to the name
      of which it is prefixed in the respective compounds
      exercised its highest valence; now, only that the element
      has a higher valence than in other similar compounds;
      thus, barium peroxide is the highest oxide of barium;
      while nitrogen and manganese peroxides, so-called, are not
      the highest oxides of those elements.