You can look things up in the Comprehensive LaTeX symbols list. It can usually be easily accessed with
texdoc symbolsortexdoc symbols-a4(in MiKTeX the latter only).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:
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.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.
Answer from Rebekah on Stack ExchangeWhy isn't my LaTeX symbol showing?
What package do I need for math symbols in LaTeX?
How do I make a symbol bigger or smaller in LaTeX?
You can look things up in the Comprehensive LaTeX symbols list. It can usually be easily accessed with
texdoc symbolsortexdoc symbols-a4(in MiKTeX the latter only).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:
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.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.
You can use Detexify to recognize symbols name, and then just google for it.
I would begin with the Comprehensive LaTex Symbols list from CTAN. Are you looking for something like \niv ? (check out page 60 of the symbols-letter.pdf.) It's in the Natural mATHematics notation package form CTAN.
More on \niv from the nath guide, pg 9:
Nath introduces \vin and \niv as names of the im- portant symbols ‘_ |’ and ‘| _ ’ not included in any standard math font.