TITLE: What is the meaning of the character "$\,\mathscr{C}\,$"?
QUESTION [0 upvotes]: The character in the circle with question mark.
Is it mean Lebesgue?
Thx for reply! :)

REPLY [1 votes]: It's a capital C, in a certain font. The TeX command to write it is \mathscr C: $\mathscr C$. As to what it means, the book ought to have told you. It is not a conventional, well-known notation that I'm aware of.
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