♯

♯ U+266F, ♯ MUSIC SHARP SIGN ← ♮ [U+266E] Miscellaneous Symbols ♰ → [U+2670]

English Wikipedia has an article on:

♯

Wikipedia

Originally a lowercase b written with a square loop (the so called "square B" or "B quadratum") to distinguish from a lowercase b written with a round loop ("round B" or "B rotundum"), when the only notes used in (Western) music were what are now considered C, D, E, F, G, A, B-flat and B. The round B was used for the former and the square B for the latter. The square B was then later generalized as the symbol for non-flat notes, variants of which diverged into the modern natural and sharp signs.

♯

1. (music) A sharp (a note one semitone higher).

In general typography, the symbol is usually written as the number sign #.

• ♭

• 𝄪 (double sharp)