What is this weird math letter?

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Occasionally I would read a mathematics paper or book and see a strange calligraphic symbol that I have no idea how to pronounce.

Like here:

Or here:

This is a problem because I, as most other people, struggle to read what I can’t pronounce even when not reading aloud.

When you encounter a symbol like this (which belongs to a family of typefaces called formal scripts), just look it up in the table below, and you’ll know what letter it stands for.

The table of formal script (“mathscr”) letters.
A \(\mathscr{A}\) N \(\mathscr{N}\)
B \(\mathscr{B}\) O \(\mathscr{O}\)
C \(\mathscr{C}\) P \(\mathscr{P}\)
D \(\mathscr{D}\) Q \(\mathscr{Q}\)
E \(\mathscr{E}\) R \(\mathscr{R}\)
F \(\mathscr{F}\) S \(\mathscr{S}\)
G \(\mathscr{G}\) T \(\mathscr{T}\)
H \(\mathscr{H}\) U \(\mathscr{U}\)
I \(\mathscr{I}\) V \(\mathscr{V}\)
J \(\mathscr{J}\) W \(\mathscr{W}\)
K \(\mathscr{K}\) X \(\mathscr{X}\)
L \(\mathscr{L}\) Y \(\mathscr{Y}\)
M \(\mathscr{M}\) Z \(\mathscr{Z}\)

Alternatively, use the excellent Detexify tool:

The formal script typeface is available in LaTeX using the \mathscr command from the mathrsfs package: