# Why doesn't logic, math, physics etc have a symbol for “example”?

We have symbols for everything but there is no symbol for "example" despite examples being fundamental to achievements.

Why is there no symbol for "example" when there are symbols for everything else?

I'd like to be able to write a formula and then have a symbol that is commonly understood to represent that what is presented is an example.

Why is this not a good idea and was not introduced?

For example:

E=hf
¤: f=3Hz... if we use ¤ as symbol for an example

• a little funny (possibly ironical, idk I'm far from 'good' at english) since you used "for example" although you're discussing condensing that phrase to a symbol :P – DanZimm Mar 31 '13 at 2:32
• I simply use, e.g., a lot, when writing, e.g. ;-), and introducing examples, here on Math.SE. – amWhy Mar 31 '13 at 2:39
• At least in math, even of a greater importance than examples seem to be counterexamples. I've found quite handy using for them ⚡e in my notes. – Leo Mar 31 '13 at 4:48
• Well, we have a string of seven symbols for it... – Qiaochu Yuan Mar 31 '13 at 6:12
• E.g. should work. – Akiva Weinberger Aug 3 '15 at 17:04

I'd hardly say "we have symbols for everything".

The reason this is not a good idea is that the word "example" is not used in any context other than its natural language meaning; in contrast, "for all", "there exists", "implies", etc. are phrases which mathematicians want to use inside the mathematics, where the symbols $\forall$, $\exists$, $\implies$ come in handy. In fact, I (for one) generally avoid even using those symbols; I'd much prefer to write $$A=\{x\in X\mid \text{ for all }y\in Y,{\scriptsize\textit{ blah blah blah }}\ldots\}$$ as long as it isn't too unwieldly to parse.

There is no added benefit to having a symbol for "example"; using a symbol that serves no purpose other than to replace an English word, outside of the mathematical content of a discussion, just creates a barrier to understanding. I mean, if you want a symbol for "example", why not have a symbol for the word "remark"? Or "conjecture"? Or "bibliography"? Or "the"?

• I wish there were a symbol for "great answer". – Elchanan Solomon Mar 31 '13 at 4:21
• I should note out that you're avoiding the informal use of the $\forall$ symbol, and that that symbol has a formal use as a quantifier where it's difficult to avoid - for instance, talking about something like the $\exists\forall\exists$ sentences of a theory is much harder without the formal symbols... – Steven Stadnicki Mar 31 '13 at 5:26
• @Steven: Yes, that's absolutely true; I was only answering the question in the context that I thought (hoped...?) the OP intended, namely, informal symbols. – Zev Chonoles Mar 31 '13 at 5:34
• @Isaac: There is, it's that red upward arrow next to Zev's answer. ;) – Raskolnikov Mar 31 '13 at 5:58
• There's also ✓, but that's only available to the asker. – Dan Mar 31 '13 at 6:39

Examples aren't in mathematics. They are tools for learning mathematics, but are exterior to mathematical systems. There couldn't be a "mathematical" symbol for it for just that reason. Granted, you could use a symbol, but it would be just a symbol that represents a word, not an acceptable character in a well-formed formula.