It's well known that X symbol means close (and in some contexts dismiss or hide), but why/where was this symbol initially chosen?   My only thought was that when you want to "cancel" information on printed paper it is crossed-out and that led to X, which is similar to crossing out an item, becoming a symbol for cancel () which was then again re-purposed as close, but I have no evidence of this. Is there a history behind this symbol?
122895
I was wondering about the reason of the choose of the X as symbol used to represents the "Close application" operation.
18684
I did not know that latex had different symbol for opening and closing quotation marks. I've used it like "abc" every where and just realised that I really should have used ``abc". Is there anyway I can convert all the quotations to become like ``abc"? Doing it manually will take forever as I have a lot of quotations.
84851
In proximity theory, we use \delta and \ll as binary relations on the power set of a set X.  How can one display NOT \delta or NOT \ll similar to how we can do \not\in.  Using \not\delta and \not\ll place the strike-through in bad positions over the \delta and \ll.  For NOT \delta, I am currently using   \!\!\not\!\delta   For NOT \ll, I am using   \hskip 0.4mm \not \hskip -0.4mm \ll   There are a few problems here.  Sometimes the placement of the "not" over the "delta" is a little off but it varies throughout the pages.  Also, at the end of the line, I may get the \not appearing at the end of the current line and the \delta appearing at the beginning of the next line.  I have not noticed this issue with my defininition of NOT \ll.  What is the best way to define these symbols?  How can one make sure that the "not" is on the same line as the "delta"?
2719
I'm reading Papadimitriou &amp; Steiglitz's Combinatorial Optimization and came across notation I'd never seen before and don't know what it means. The $\LaTeX$ markup for it is \gtrless ($\gtrless$), which took me quite a while to find.  It arises in the formulation of general linear programs in terms of the constraints on the variables:  $$ x_j \geq 0 \;\; j \in N\\ x_j \gtrless 0 \;\; j \in \bar{N} $$  It's not "not equals" because there's places in the text where the authors say $x$ can be zero.
105238
I was wondering if someone knows if there is a foot/feet symbol available in any of latex packages that I could use in my text? I would appreciate any hint.  I do really mean a foot/feet icon as in the picture below.
120791
In some texts (mainly complex analysis or harmonic analysis) I sometimes see the following double subset symbol $\subset\subset$ for inclusion relation of two regions, e.g., $\Omega$ and $\Omega'$ are two regions in $\mathbb{C}$ such that $\Omega \subset\subset \Omega'$. I never figured out what it means exactly; I always interpreted it as the closure $\overline{\Omega}$ is contained in $\Omega'$ (so that some nasty boundary effects can be avoided). Is that right? Or does $\subset\subset$ mean some other kind of inclusion? Thanks.
115161
Regard this statement $ x \ge 0$. According to my teacher, by negating this statement, it will become $ x &lt; 0$. Why is this so; why does the $\ge$ morph into $&lt;$, and not into $\le$?
116712
When writing an integral, it seems like something should be done to separate the "d", as in \int f(x) dx, so as not to confuse it with a variable. I've seen it left as-is, bolded, and straightened. Even among those options there are several ways to accomplish each task; e.g., I could do a \mathrm or a \operatorname. What is the preferred method of dealing with the "d"?
119026
I've been googleing and ran across  little blog post. It has a bit of information stating the the &amp; symbol was at one point the 27th letter in the alphabet.     For years the &amp; symbol (now known as the ampersand) was the final,   pronounced “and” but recited with the Latin “per se,” meaning “by   itself.” The position and pronunciation eventually ran together, with   “X, Y, Z, and per se and” becoming “X, Y, Z, ampersand.”   I have to wonder how could a symbol be in the alphabet? My understanding is that letters represent sounds and the putting the sounds together make words. If &amp; was a letter for the combined sound that the word "and" makes was it ever used in the spelling of a word? Something along the lines of “h&amp;” for hand? Also, why was &amp; in the alphabet and not other symbols like % or #?  I don't think this is a duplicate as I'm not looking for the definition of the &amp; symbol or the story of where it came from but rather its use as a letter in the alphabet and any words that used it in their spelling. The linked blog states it was the 27th letter but gives no examples of word usage.
70010
In order to write a scientific paper, I would like to use the symbol     \rightsquigarrow or \leadsto   which look as: $\rightsquigarrow$ or $\leadsto$  I'm wondering about the usual meaning and use of this symbol.  Thanks in advance.
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I would like to reproduce the following symbol:     The  does not seem to refer to that symbol, I did not find any font corresponding in the  by Michael Sharpe My pdf reader tells me that the embedded fonts are      But that is related to the OCR technique and does probably not reflect the font actually used.    was not really conclusive:        and  were of no help. I did not manage to find it in the  nor in the    Does someone have an idea? Do I miss something?  EDIT: in context,   EDIT 2: when I copy / paste that symbol from my pdf viewer, it yields a 2, could that be a 2? It really looks like an L!  That also is probably related to some error of the OCR.
56773
Could someone please tell me what the symbol ringed in red represents?     I know it has ON Switch pointing to it, but the symbol has other lables in different parts of the document.
57136
I've occasionally seen a negative (when a number is simply negative, not a subtraction), typeset as negative sign that's slightly skinnier and above the centre line of text. Is this proper notation for mathematics and how would one go about typesetting this in LaTeX?   Edit  I believe that calculators were what happened to give me this idea, couldn't find it in any of my math books. Thank you all for the help, it's much appreciated.     Thank you 'Antal S-Z' for the photo link.  However, the question remains, how exactly would I typeset this?
60318
I'd like to put one symbol over another? There are some similar things in math, like $\binom{a}{b}$, but I don't want the parentheses, or $\frac{a}{b}$ without the division line.  The closest I've found is $\overset{a}{b}$ (from mathtools) but the a ends up smaller than the b.
116855
I can't draw a particular cross symbol in LaTeX.  I tried drawing it in Dextify, but that didn't recognize the symbol.  I don't even know what it is called.  Any help with the name or the code is appreciated.  An image is below.
89914
Examples  I've recently found examples of using pairs of enclosing braces {}, with nothing in between the opening and closing braces, as arguments to commands and even to their options:  cat foo | xargs -I{} echo {}  find . -size 0 -exec rm -i {} \;  No Documentation  My problem is that I cannot find a documentation in the  that describes the usage of {} in such context as in the examples above.  I do not think it is a , because a dollar sign must precede the enclosing braces in a parameter expansion as in ${}.  It cannot be a  either, because it takes the form of {x..y[..incr]}, where x and y are not optional.  It also cannot be a  either, because {} is used as arguments.  Questions   What does a pair of enclosing braces {} even mean, in general, as an argument to any command that accepts it? Where can I find a documentation that describes the usage of {} as arguments?
28119
What is the "best LaTeX practices" for writing absolute value symbols?  Are there any packages which provide good methods?  Some options include |x| and \mid x \mid, but I'm not sure which is best...