What 𝙴 means
Its style can matter inside a formula. A math E and plain E may stand for different quantities; the formula tells you what each means.
Why does mathematical monospace E have its own character?
Mathematical style can distinguish symbols. In 1999, the STIX project (Scientific and Technical Information Exchange), a collaboration on math fonts, proposed separate Unicode alphabets for mathematical styles, including monospace. Unicode already had a few styled math letters in its Letterlike Symbols collection; the proposal extended them into alphabets so plain text could retain their distinctions.
Why can 𝙴 turn into plain E?
Some Unicode text cleanup can remove its style. NFKC and NFKD, Unicode's compatibility forms, turn 𝙴 into plain E; NFC and NFD preserve it.
Don't confuse it with
4Questions people ask
1Why does 𝙴 show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type 𝙴
𝙴\1D674Codes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.