What ⟪ means
It marks the opening edge. In typeset math, ⟪ and ⟫ fence an expression. Its Unicode alias links it to Z notation, a formal method for specifying systems, where angle brackets mark definitions.
A printed book attributed to Josse Bade’s press uses guillemets for quotation in 1527. In 1634, mathematician Pierre Hérigone used angle symbols and the less-than sign in a mathematical work.
Don't confuse it with
2Questions people ask
1Can the pair expand around a tall formula?
Yes. Mathematical fences can grow to fit an expression.
How to type ⟪
Windows (Word)
Alt+XType 27EA, then Alt+X to get ⟪.
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 “mathematical left double angle bracket”.
Linux
Ctrl+Shift+UType 27ea, then Enter or Space.
HTML
⟪CSS
\27EALinux Unicode input
On Linux systems with Unicode entry, press Ctrl+Shift+U, type 27EA, then press Enter.
Codes and encoding1 code points
HTML decimal
⟪
HTML hex
⟪
CSS content
content: "\27EA";
Each escape is closed by the next backslash; a trailing space is needed before a literal hex digit.
URL encoded
%E2%9F%AA
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.