Just want to know how to type this symbol in Latex. I saw it used in the axioms of probability. Thanks.
\usepackage{amssymb}
\mathfrak{F}
Euler fraktur bold
\usepackage{amssymb}and\mathfrak{F}should do. – egreg May 03 '14 at 23:23Euler fraktur bold(see http://tex.stackexchange.com/questions/58098/what-are-all-the-font-styles-i-can-use-in-math-mode). – Karlo Nov 04 '15 at 09:15