\flatThe \flat symbol is used in mathematics and music notation. In mathematics, it can denote a flat module or a flat morphism in algebraic geometry. In music, it indicates that a note is to be lowered by a semitone.
A musical note A lowered by a semitone.
A^\flatA flat module in algebra.
M_\flatA flat morphism in algebraic geometry.
f^\flat: Y \to X