# What does $\therefore$ mean

Question: I recently read the symbol $\therefore$ in a couple of posts. Unfortunately i can't find the posts anymore. Does this have any special mathematical meaning?

• I put the symbol he meant in LaTeX, I'm not so sure this is appropriate. Please offer comments. – user223391 Dec 26 '15 at 3:09
• Im fine with that, maybe this makes searching this question hard, but probably there are few people having this question anyway... – math635 Dec 26 '15 at 3:15
• @avid19 I thought about doing that too, but I think that this undermines the purpose of reference for people with this question. Since even in detexify.org this symbol, when drawn, sometimes appears quite down on the "show more" option, maybe this question may serve as useful reference indeed. – Aloizio Macedo Dec 26 '15 at 5:19

I think you are referring to $\therefore$
• @math635 No, I don't know the historical reason for this. It is worth saying that the inverted triangle $\because$ is usually a shorthand for "because". The wikipedia entry says that the notation is due to Johann Rahn, but does not explain a specific reason for the adopted notation. I would guess there is no great reason, only a symbolic shorthand necessity. – Aloizio Macedo Dec 26 '15 at 2:58
• archive.org/details/historyofmathema031756mbp should be of help. IIRC \therefore: $\therefore$, and \because: $\because$ were used in a confusing, often interchanged manner for ages until a couple of British translations of Euclid settled the matter. – stochasticboy321 Dec 26 '15 at 3:00
The notation $\therefore$ (written as \therefore) is shorthand for the word therefore. Since the symbol connects cause and effect, the symbol is pretty common and thus has a common abbreviation. This link has a list of more logic symbols, such as $\forall$ (for all). Also, the upside-down version of the symbol is used to mean "because"