You think I'm joking, right? I'm not. Think of the keywords that apply to the title. "OpenCV" and "circle" definitely are. I don't consider "detect" and "image

You think I'm joking, right? I'm not. Think of the keywords that apply to the title. "OpenCV" and "circle" definitely are. I don't consider "detect" and "image" as keywords here because if you are using OpenCV, there's a very high probability that you want to detect something in an image. So "detect" and "image" are pretty much implied by "OpenCV". And I'm going to give you the benefit of doubt and include "red" as a keyword. So we end up with "OpenCV", "circle", and "red". Three keywords. "circle" being technically wrong means that you got 1/3 of the keywords wrong. That's actually no small mistake. Let's say you are working on a project and you are in urgent need to find out how to use OpenCV to effectively detect actual circles (not red discs). You type these keywords into your favourite search engine: ["opencv", "circle"]. And you get this article as the top result because it has the right keywords and it ranks high in popularity. Then congratulations, you just wasted your precious time. Of course, you can start from this article and get to your correct solution. But remember I said that you're in urgent need, you're in a hurry, you don't have time to waste. The converse is also true: you want to detect actual red discs but you can't find this article because the article's keywords are wrong. When I saw the title of the article, I really was expecting it to talk about detecting circles, not discs. I started at the beginning and I thought "ok, maybe the author's approach is to start from discs and eventually get to circles". I followed through to the end expecting to see actual circles, but then... nothing. I was really disappointed. I could be even more pedantic and point out that in mathematics, a circle has no width, but if we take that extra pedantic definition, then we won't expect to detect anything at all in an image. The difference here is that when we talk about "circle", we know that we are really talking about an approximate representation of a circle. But a circle is not an approximate representation of a disc, or vice versa, period.