I was looking through HTML entities and ran across ℱ. I searched for all entities ending in trf; and also found ℳ, ℒ, and ℨ.
Apparently “trf” stands “transform” and these symbols are intended to be used to represent the Fourier transform, Mellin transform, Laplace transform, and z-transform.
You would not know from the Unicode names that these symbols are intended to be used for transforms. For example, U+2131 has Unicode name SCRIPT CAPITAL F. But the HTML entity ℱ suggests how the symbol could be used.
These are not the symbols I’d use for these transforms if I had access to LaTeX. I’d use {\cal F} for the Fourier transform, for example. But if I were writing about math and restricted to Unicode symbols, as I am on Twitter, I might use these symbols. I could imagine, for example, using ℒ for Laplace transform on @AnalysisFact.
Here’s a table with more on the four transform symbols that have HTML entities.
