Mathematical Bold Script Small U

It is a separate math letter, but it has no fixed value. Think of it as a lowercase Latin u drawn in a heavier script style. In a formula, a writer can use that style to separate one quantity from plain u; the equation supplies the actual meaning.

Why is 𝓾 a separate character?

It keeps mathematical differences intact in plain text. Mathematics already used upright, italic, bold, and script lettering to distinguish notation. The STIX project—a publisher-led effort to build fonts for research publishing—proposed complete calligraphic and bold-calligraphic Latin alphabets to Unicode in 1999. The proposal explains that flattening styled letters can change a formula. These alphabets also extended Unicode’s older collection of isolated letterlike symbols into fuller mathematical sets. Unicode reserves them for mathematical or technical notation, not as a substitute for bold styling in ordinary prose.

A compatibility-normalization cleanup can turn 𝓾 into plain u. That is useful when software needs to treat it as an ordinary letter, but it erases the mathematical distinction.

Why does 𝓾 look different across fonts?

The font can change its script letterform. Unicode’s chart is a sample, not a fixed drawing template; script forms vary among mathematical fonts. The underlying character stays 𝓾 even when its loops or weight differ.