I was talking with a friend of mine when she told me that "pretty sure" means something like "more or less sure". I've always known that it meant "totally sure" and was astonished to find this out.

Thinking about it, I could not remember why or how I learned the wrong meaning and looking on the Internet I found more people that thought the same before being corrected.

Edit: I do know that there is a question answering the meaning of the expression. What I'm trying to find out with this one is the reason why some people like me learned the wrong meaning and was sure it was correct. Sorry if I wasn't clear enough.

What could be the origin of such misunderstanding?

  • I wonder if the “why” wouldn’t be better asked on Language Learning. It’s fairly common for people to get a slightly wrong interpretation of a phrase when we’re learning from context instead of dictionaries. I’m not sure that explaining why a phrase is commonly misunderstood is something we can help with though. – ColleenV parted ways Jan 7 '19 at 11:38
  • I'm pretty sure that such misunderstandings arise as a consequence normal human error. – Strawberry May 10 '19 at 8:58

Pretty sure does NOT mean totally sure - that's to say certain. If some people think differently, they've been misled.

Adding pretty is a way of hedging your bets when you express an opinion but want to leave yourself with a get-out in case you're wrong.

It's equivalent to saying I'm almost sure.

I'm pretty sure I locked the door when we left

leaves you with room to apologise if you find out that you're wrong

I'm totally sure (or **certain) commits you

Get it wrong and you may well be in trouble.

You're not the first to ask the question on this site and may well find it closed as the answer has previously been given. Best check next time before you ask.

What does "I'm pretty sure" mean?

  • I know that the question you pointed out exists. My question was to know why such misunderstanding exists, so I don't think this question is a duplicate of the other. Sorry if I was not clear enough, I'll edit my question to clarify. – Douglas Santos Jan 7 '19 at 8:46
  • @DouglasSantos The question of how such misunderstandings arise in certain parts of the world is beyond the scope of this site. I regret that you will have to look elsewhere for an answer. – Ronald Sole Jan 7 '19 at 10:15

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