Mathematical symbols for common phrases such as $\textit{for some}$ and $\textit{such that}$

Question

I noticed that I use the phrases $\textit{for some}$ and $\textit{such that}$ a lot in pretty much every proof.

Here is an example of the use of $\textit{for some}$:

$\textit{The range of a function is defined as:}$

$$f(X) = \left \{ y \in Y \ | \ y = f(x) \ \text{for some} \ x \in X \right \}.$$

Are there common mathematical symbols for those phrases similar to $\exists \ \text{and} \ \forall$?

"for some" is the same as $\exists$ if I understand you correctly. there are a few for "such that" but the phrase itself is usually used, or sometimes "s.t." in notes, but not formally. — The Count, Mar 21 '17 at 18:23
@TheCount I added an example of the use of $\textit{for some}$. — user6005857, Mar 21 '17 at 18:28
You could say $f(X) = \left { y \in Y \ | \ \exists x\in X ;\text{such that}; y = f(x)\right }.$ But I agree, your way is a little nicer, and a symbol would be nice. I know of none. — The Count, Mar 21 '17 at 18:30
These days there's a symbol for everything. But just because you can use a symbol doesn't mean you should. — Robert Soupe, Mar 21 '17 at 20:33
There's also $\Rightarrow$ for "implies", $\land$ for "and", and $\lor$ for "or". — Shaun, Mar 23 '17 at 16:49

Michael Hardy · Answer 1 · 2017-03-21T19:19:43.620

If I needed or wanted to use terse symbols, I would render $\text{“} y = f(x)$ for some $x\in X\text{''}$ as $$ \exists x\in X\ y = f(x). $$

(A typographical note: In MathJax and LaTeX in expressions like $\forall\varepsilon\, \exists\delta\,[\cdots\cdots],$ I manually add a bit of space after $\forall\varepsilon$ and after $\exists\delta$ for reasons that I expect will be clear by hindisight, although I sometimes see this neglected by those who use MathJax and LaTeX.)

score 3 · Accepted Answer · answered Mar 21 '17 at 18:50

3

You can read $\{y\in Y\mid \exists x\in X, y=f (x)\}$ as "the set of all $y\in Y$ such that $y=f (x)$ for some $x\in X$"; essentially, $\mid$ can function as "such that" in that context.

A simple "s. t. " is often understood as "such that" too.

answered Mar 21 '17 at 18:50

Shaun

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Mathematical symbols for common phrases such as $\textit{for some}$ and $\textit{such that}$

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