from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. An argument or consideration in favor of something: weighing the pros and cons.
  • n. One who supports a proposal or takes the affirmative side in a debate.
  • adv. In favor; affirmatively: arguing pro and con.
  • adj. Affirmative; supporting: a pro vote.
  • n. A professional, especially in sports.
  • n. An expert in a field of endeavor.
  • adj. Professional: pro football.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. an advantage of something, especially when contrasted with its disadvantages (cons).
  • prep. In favor of
  • n. a professional sportsman
  • n. professional someone who is very good at something
  • n. A prostitute.
  • abbr. ISO 639 code for Old Provençal

from the GNU version of the Collaborative International Dictionary of English

  • adv. For, on, or in behalf of, the affirmative side; -- in contrast with con.
  • prep. A Latin preposition signifying for, before, forth.

from The Century Dictionary and Cyclopedia

  • n. A Latin preposition occurring in several phrases used in English.
  • n. A prefix of Latin or Greek origin, meaning ‘before,’ ‘in front,’ ‘fore,’ ‘forth,’ ‘forward.’ In some words, as proconsul, proprætor, pronoun, etc., it is properly the preposition (Latin pro, for, instead of).

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adv. in favor of a proposition, opinion, etc.
  • n. an argument in favor of a proposal
  • adj. in favor of (an action or proposal etc.)
  • n. an athlete who plays for pay


Middle English, from Latin prō, for.
(American Heritage® Dictionary of the English Language, Fourth Edition)
from Provencal (Wiktionary)
From Latin prō ("on behalf of"). (Wiktionary)
Shortening. (Wiktionary)



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  • "About 15 years later, Loeb had another brain wave. He realised that their design could be exploited to generate power. Working at Ben-Gurion University of the Negev, in Beer Sheva, Israel, he envisaged a tank with two chambers separated by a semipermeable membrane. With saltwater on one side and fresh on the other, osmosis would draw fresh water into the salty side, raising its pressure. This pressurised saltwater could then be piped through a turbine to generate electricity (see diagram). Loeb named this process pressure retarded osmosis (PRO) and patented it in 1973."
    - Kate Ravilious, Salt solution: Cheap power from the river's mouth,, 25 Feb 2009.

    April 8, 2009