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

1. You can look things up in the Comprehensive LaTeX symbols list. It can usually be easily accessed with texdoc symbols or texdoc symbols-a4 (in MiKTeX the latter only).

2. Another good option is to try the web-based software Detexify, which allows you to draw the symbol and tries to recognize what you've drawn. Here is a screenshot:

   

3. If you are using the package unicode-math, then besides using any Unicode character list, the list of all supported symbols (texdoc unimath-symbols) is very useful as it also lists which symbols are available in the various fonts.

4. Using unicode-math, you can also search for characters by drawing (just like with detexify) using ShapeCatcher.

_{The above techniques provide an adequate way of finding symbols but are not necessarily foolproof since you sometimes need to know what you're looking for in order to find it. For example, in Typing Following notation in Latex it may not be apparent that "vector fields in differential geometry" are somehow related to "bowties". To that end, searching for a symbol rotated 90 degrees or flipped horizontally, say, might lead you in the right direction.}

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.