Mathematical Script Capital T

It names a variable or object in a mathematical formula. Mathematical writing uses letter styles as separate labels; Unicode gives this styled letter its own character so the distinction can survive as text. In topology, 𝒯 commonly denotes a topology: a collection of subsets—parts of a set—called open sets. In another field, follow the author's definition.

Why does 𝒯 look different?

Its default drawing follows the math font. Unicode 18.0 lists two optional styles for this capital: chancery, a flowing calligraphic hand, and roundhand, a rounder hand-lettered style. Selectors FE00 and FE01 request them; without a selector, the font supplies its default form.