How to look up a symbol or identify a letter from a math alphabet or other character?

This reference has yet to fail me; it has all the symbols typeset along with the foo command needed to generate them. There's also this PDF, which is considerably better put-together and covers other symbols besides the base math ones

Theres lots of ways of doing this, but the two I've found to be most useful are these:

• Detexify Allows you to draw the symbol, and then guesses based on similar symbols. This is great for me because I don't always remember the name of the symbol, and even if I know the name, I may not have the correct name.

• AMS LaTeX Short Math Guide This short pdf gives an overview of AMS LaTeX functionality, and includes a pretty thorough list of most of the math symbols (un)commonly used in proofs and formulas.

The old school way is to look it up in the Comprehensive LaTeX Symbol List (warning: 4 MB PDF file).

The new hotness is to use DeTeXify which uses handwriting recognition to look the symbol up for you.

DeTeXify even comes in an iPhone/Andriod app- you can get a free version or pay for one. The only difference is that with the paid app you are making a donation to the developer- the feature set is exactly the same.

The author is planning to work on a mobile version of the website that will supplant these apps.

I often look up the relevant topic on Wikipedia, (e.g. Set theory) and look at the source there. Wikipedia uses LaTeX for math markup as well.

There's also an iPhone app for Detexify, which I've used occasionally, for some reason ...

Links (on the US iTunes App Store): free version and supporter version ($0.99, same functionality).

The LaTeX wikibook Mathematics section has been very helpful for me.

For uncommon symbols, instead of search documentation on-line or in a big PDF to find packages and commands to include in my code, I have found useful sometimes to compile the whole table of characters of a font (even in the working document) to quickly find, for example, the skull of the omding font that is char194. Of course, you have first to know that you have a font file with that name (omding.tfm) but then is easy:

documentclass{article}
usepackage{fonttable}
begin{document}
fonttable{omding}
fontomding=omding
omding  char194
end{document}

You can also search for a skull the in Comprehensive LaTeX symbols list, or paint a skull in Detexify, or remember the easy command "skull" (and do not forget load the skull package and enter in math mode) o try to find a dingbat or ding{whatever}... but when I want a skull (really never) must be that of white bones (just try the other methods if you don't know what I mean).

Some utilities for lookup symbols in Unicode:

• ent2latex: A Perl script to translate Unicode symbols to LaTeX commands. (However, it doesn't utilize math fonts.)

• kcharset: A KDE application to lookup Unicode. (Well, you can input some symbols in Unicode directly, or lookup the corresponding LaTeX command by ent2latex.)

I've just come across this list http://milde.users.sourceforge.net/LUCR/Math/unimathsymbols.pdf which lists characters using unicode numbers, their representation, and their (La)TeX command, together with other useful information.

Here's a random sample of what it looks like:

I use the Daum Equation editor then just copy and paste the code at the bottom (you can specify Tex,LaTeX, etc.) and even favourite the equations/symbols to avoid having to re-look them up every time you use them. Not sure if they have EVERY symbol, but it has been a good reference for me so far!

TL;DR

Direct link to the online service

This service allows classification by drawing (even works on mobile devices!) and by text:

Some information

The handwriting recognition toolkit (hwrt) is one possibility to classify you recordings. There are still many rough edges and the software gets updated on a daily basis (04.12.2014). The user interface is in a browser and looks like this:

The installation is explained in the documentation. If you have trouble or have an idea how to improve it, just leave a comment or write an email ([email protected]).

This is a part of my bachelor's thesis. The thesis, some presentations and links to all software projects are on http://martin-thoma.com/write-math/

In case you are using TeXstudio or Texmaker, you can browse the built-in catalog of symbols and find the symbol you need in the appropriate category of symbols (see the image below). It is very convenient, as by clicking on the symbol it gets automatically inserted into your document.

Moreover, if you're using TeXstudio on Windows, you can use Wizards -> Math Assistant... which enables you to draw symbols and it translates them into text.

My book "Schnell and Ziel mit LaTeX2e" (only available in German) has a symbol index with a lookup method inspired by Chinese dictionaries: The mathematical symbols are ordered by the number and type of strokes needed to draw them. The index includes the symbols from plain TeX, AMS symbols, and LaTeX symbols.

As far as I know, this index has not been copied by other authors.

fontawesome provides access to a host of web-related icons (or symbols) provided by the included Font Awesome font.

documentclass{article}

usepackage{fontawesome}

setlength{parindent}{0pt}% Just for this example

begin{document}

These are some symbols from the font texttt{FontAwesome}:

faBicycle
faCodeFork
faDiamond
faFirefox
faFortAwesome
faGears
faJsfiddle
faLinux

end{document}

However, if you want access to the latest-and-greatest web-related icons from the font and are running XeLaTeX or LuaLaTeX, you can download the font directly. Here you can also search the list of available icons to identify a symbol.

documentclass{article}

usepackage{fontspec}

newfontfamily{fa}{FontAwesome_0.otf}% http://fontawesome.io/

setlength{parindent}{0pt}% Just for this example

begin{document}

These are some symbols from the font texttt{FontAwesome}:

fa
symbol{"F2B9} % http://fontawesome.io/icon/address-book/
symbol{"F2DC} % http://fontawesome.io/icon/snowflake-o/
symbol{"F2C5} % http://fontawesome.io/icon/free-code-camp/
symbol{"F2CC} % http://fontawesome.io/icon/shower/
symbol{"F2DD} % http://fontawesome.io/icon/superpowers/
symbol{"F2D6} % http://fontawesome.io/icon/grav/
symbol{"F2C6} % http://fontawesome.io/icon/telegram/
symbol{"F2CE} % http://fontawesome.io/icon/podcast/

end{document}

If you use Mac, there is an app named "Texpad 2" from which you can pick most symbols:

To the long list of answers provided how to identify a character using online tools I can suggest to use also:

• Shapecatcher very similar to Detexify, where you can find in addition to Unicode characters also LaTeX characters (see the symbol of the beta near the chick).
• Drawing Font Checker by Tekla apparently free software that allows you to detect fonts using an image.

Referring to the answer of the user @Werner, there is also a supplement as increased of the package fontawesome, called fontawesome5 of Marcel Krüger.

This is a small table as example,

documentclass[a4paper,12pt]{article}
usepackage{fontawesome5}
begin{document}
begin{table}
centering
caption{Some fontawesome5 symbols}
medskip
begin{tabular}{|l|l|}
hline
faArtstation & faAtom  hline
faGoogleDrive &  faBowlingBall  hline
faBroom &  faCarrot hline
faCheese &  faFrog hline
end{tabular}
end{table}
end{document}