The phrase pros and cons has given me an illusion for a long time that pro means something good (supporting, approving, agreeing), while con means something bad (trick, hoax, disadvantage):

  • promising, prosperous, professional, ...
  • contradict, confront, concede, ...

However, when append -stitution to both words, they turn into prostitution and constitution. I checked their spellings carefully and can confirm that these 12-letter words are absolutely the same except for the first 3 letters. That is an overwhelming 75% similarity. This confused me, you know, because people often regard constitution as a word giving more positive sentiment than prostitution. (You may or may not agree with this.)

How were these two words formed historically? Is it a stereotype that pro means good while con means bad? What does it mean if somebody calls me a pro? Do they genuinely 100%-time mean that I am a professional player, but not a prostitute in any slightest sense?

1 Answer 1


Pros and cons comes from the Latin prefixes "pro" and "contra" which mean "for" and "against," respectively.

The Latin prefix "con-" (which is not the same as "contra") means "with."

Constitute and prostitute share the Latin root "statuo" which has a broad range of meanings, including set up, establish, determine, erect, decide, hold up.

The idea that pro- words are always good and con- words are always bad is wrong.

For just a few examples that break your stereotypes:

  • Confidence, convivial, connect, contemporary, conservation
  • Problem, prohibition, procrastinate, provoke, propaganda

If someone calls you a "pro" at something, barring any unusual facts about your employment, it's highly unlikely that they're calling you either a professional sports player or a prostitute. Generally, they're just saying you're talented at something, possibly to the point of being able to make a living off that skill.

  • One side of the question ("con" words): The Latin prefix "con-" is in point, I think. Given the "con-" in "constitute" comes from "con-" not "contra-", "establish together" explains "constitute" well. "con-" can be a neutral prefix, the compound word formed from which also depends on the other part.
    – Cyker
    Commented Dec 7, 2019 at 9:52
  • The other side ("pro" words): What I found was "pro-" can also mean "before" and "front", besides "favor" and "like". This applies to "prohibition", "provoke", etc. If so it's not clear whether the word is good or bad by looking at "pro-" alone. But I think "pro-" in "procrastinate" means "favor" not "front". It basically means "I like tomorrow".
    – Cyker
    Commented Dec 7, 2019 at 10:03
  • 1
    @Cyker You have failed to understand the point: you can't tell just by looking at the prefix whether the word has a positive, negative or neutral valence.
    – Katy
    Commented Dec 7, 2019 at 10:04
  • Well, I think prefix carries a meaning. But some prefix carries multiple meanings, and one or more of those could be neutral. That's why the meaning of the whole word sometimes depends more on what follows the prefix. So one can't say "pro-" words are always good, while those good "pro-" words do have relationship.
    – Cyker
    Commented Dec 7, 2019 at 10:13
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    @Cyker And if 'conforming to etymology' were the sole basis on which we judged word usage, I could say I was an automobile, because I move myself around. But it isn't, and we can't.
    – Katy
    Commented Dec 7, 2019 at 10:32

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