# What is the correct symbol to use for ending a counterexample?

I am familiar with the tombstone symbol, "$\blacksquare$", that is used to signify the end of a proof. However, it is my understanding that an example isn't technically a proof. For instance, one can't just find an example of a proposition being true and then claim the proposition to be true.

So, I was wondering if there is a symbol that should be used to signify the end of a counterexample?

• Currently your question is only tangentially related to math education, if it is at all. Can you edit it to explain how it is a question about education rather than a mathematical or historical one? Or maybe the question would be better at math.SE instead. – Chris Cunningham Apr 10 '18 at 20:25
• @ChrisCunninham What is the difference between math.SE and math education? – Jordan Apr 10 '18 at 21:18
• @Jordan Math SE is about math, and Math Educators is about teaching math. If you're currently writing a journal article, your question is off-topic in Math Educators; if you're currently writing a textbook or lecture notes, it may be on-topic. – Uwe Apr 10 '18 at 23:09
• @Uwe Ah, I see, I am very off topic then. I will see about removing this question. :) – Jordan Apr 10 '18 at 23:12

• (+1) I would also like to add that I, personally, like to use $\square$ for the end of a proof, example, or counterexample. When I read a paper, I can put a little check in that box when I grok it. :) – Xander Henderson Apr 10 '18 at 16:15