The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

   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.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Per \Per\, prep. [L. Cf. Far, For-, Pardon, and cf. Par,
   prep.]
   Through; by means of; through the agency of; by; for; for
   each; as, per annum; per capita, by heads, or according to
   individuals; per curiam, by the court; per se, by itself, of
   itself. Per is also sometimes used with English words.
   [1913 Webster]

   Per annum, by the year; in each successive year; annually.


   per cent, Per centum, percent, by the hundred; in the
      hundred; a proportion multiplied by one hundred; -- used
      esp. of proportions of ingredients, rate or amount of
      interest, and the like; most commonly used in the
      shortened form per cent; as, 5 is ten per cent of 50. It
      is commonly symbolized with the per cent sign, "%".

   Per diem, by the day. [For other phrases from the Latin,
      see Quotations, Phrases, etc., from Foreign Languages, in
      the Supplement.]
      [1913 Webster]

The Free On-line Dictionary of Computing (19 January 2023):

PER

   1.  Packed Encoding Rules.

   2.  partial equivalence relation.

   (1998-05-27)