# Is there a sign for “according to?”

There are signs in mathematics for "therefore" and "because," which are $\therefore$ and $\because$ respectively.

However, another frequently-used expression is "according to." Is there any symbol for that?

• Do you mean it like "according to [reference]" or "according to Eq. (X)", or something mathematical? Could you provide an example? – Bobson Dugnutt Sep 4 '16 at 17:24
• @Lovsovs I mean both, as a matter of fact. I would have thought that it would be the same, but even if it isn't I'd like to know, as I haven't come across anything like it before. – Skeleton Bow Sep 4 '16 at 17:30
• Sometimes the clearest route is simply using "according to...". Clarity isn't guaranteed by finding symbolic notation for every notion. When meaning is dependent on context (according to Plato...), according to figure 1.a..., etc – amWhy Sep 4 '16 at 17:31
• Don't be afraid to use some actual words. – amWhy Sep 4 '16 at 17:33
• Instead of "according to Eq. $(3)$", you can also often write "by Eq. $(3)$". Less typing, and using both gives additional variation of formulation. – Daniel Fischer Sep 4 '16 at 17:58

No, there isn't, and it isn't good practice to use mathematical/formalistic symbols in the middle of a sentence.

For instance:

"Now, Eq. (1) $\rightarrow$ that Eq. (2) is $\sim$ true,"

"Now, Eq. (1) implies that Eq. (2) is false,"

only makes the sentence more obscure. You could write out every sentence as a logical statement, but ask yourself, "what text would I rather read?" Your audience probably would choose the same.

• Thanks for the answer. On a side note, should I use a single or a double arrow for "implies that?" – Skeleton Bow Sep 4 '16 at 17:37
• @SkeletonBow Single; the double is a "double implication," which has a different (stronger) meaning. – Bobson Dugnutt Sep 4 '16 at 17:38
• @Lovsovs OP means "$\implies$" versus "$\to$", perhaps. – Pedro Tamaroff Sep 4 '16 at 17:54
• @Lovsovs What’s the meaning of the double implication? Oh, you mean the equivalence arrow “⇔”, right? – k.stm Sep 4 '16 at 17:55
• @SkeletonBow They often mean the same, but when doing some algebraic manipulations, I'd actually stick to using $\implies$. $\rightarrow$ can also be used, but is also used when defining functions ($f:\mathbb{R}\rightarrow \mathbb{R}^2$). See this wiki for more details. – Bobson Dugnutt Sep 4 '16 at 18:44

There is a Latin abbreviation sec. from secundum, meaning "following" or "in accordance with", sometimes used as "sec. Smith", which means "according to Smith".

• Interesting! Would it be applicable for something like sec. Eq (1) or sec. [reference to rule]? – Skeleton Bow Sep 4 '16 at 21:58
• @SkeletonBow I have no idea! If not for my exceptional google-fu, I wouldn't even know about this abbreviation. ;) – dbanet Sep 4 '16 at 22:02
• @SkeletonBow : You should only use this abbreviation if you do not want people to know what you mean. – Michael Sep 5 '16 at 3:10