1. a prefix meaning “through,” “thoroughly,” “utterly,” “very”: pervert; pervade; perfect.
  2. Chemistry. a prefix used in the names of inorganic acids and their salts that possess the maximum amount of the element specified in the base word: percarbonic (H2C2O5), permanganic (HMnO4), persulfuric (H2S2O8), acids; potassium permanganate (KMnO4); potassium persulfate (K2S2O8).

Origin of per-

< Latin, combining form of per per, and used as an intensive Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for per-


  1. throughpervade
  2. throughoutperennial
  3. away, beyondperfidy
  4. completely, throughlyperplex
  5. (intensifier)perfervid
  6. indicating that a chemical compound contains a high proportion of a specified elementperoxide; perchloride
  7. indicating that a chemical element is in a higher than usual state of oxidationpermanganate; perchlorate
  8. (not in technical usage) a variant of peroxy- persulphuric acid

Word Origin for per-

from Latin per through
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for per-

word-forming element meaning "through, throughout; thoroughly; entirely, utterly," from Latin preposition per (see per (prep.)).

Online Etymology Dictionary, © 2010 Douglas Harper

per- in Medicine


  1. Thoroughly; completely; intensely:perfuse.
  2. Containing an element in its highest oxidation state:perchloric acid.
  3. Containing a large or the largest possible proportion of an element:peroxide.
  4. Containing the peroxy group:peracid.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.