What's the name of this letter? [closed]

I came upon this letter when reading a book, I couldn't find its name on the internet, you can imagine how hard it is to search about it.

What is the name of the letter that follows "sample space"?

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I know it's not really an English question, but I think this site is best fit for the question than say, the mathematics site.


Solution 1:

It's an S written in a fraktur font used by mathematicians. This one is easy to find out using Detexify.