What ⅇ means
It marks e as the base of natural logarithms.
In 2002, Unicode described it among a few signs used for constants and differential notation in specialist mathematical publishing, including patent applications.
Don't confuse it with
4Questions people ask
1Can an italic e replace ⅇ?
Sometimes. Math layout can italicize a plain e; use ⅇ when the formula or document specifies that distinct character.
How to type ⅇ
Windows (Word)
Alt+XType 2147, then Alt+X to get ⅇ.
Windows
Win+Rrun charmap for the full table, or use the emoji picker's Ω symbols tab (Win + .).
macOS
Control+Command+SpaceOpen the character viewer and search “double-struck italic small e”.
Linux
Ctrl+Shift+UType 2147, then Enter or Space.
HTML
ⅇCSS
\2147Codes and encoding1 code points
HTML decimal
ⅇ
HTML hex
ⅇ
CSS content
content: "\2147";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%85%87
1
On screen
1
Code points
1
JS .length
3
UTF-8 bytes
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.