Unicode: 21CB. Infix arrow-like operator. x ⇋ y is by default interpreted as ReverseEquilibrium[x,y]. Extensible character.
Unicode: 2035. Alias: Esc ` Esc. Letter-like form. Used in an overscript position as a grave accent.
Unicode: 296F. Infix arrow-like operator. x ⥯ y is by default interpreted as ReverseUpEquilibrium[x,y]. Extensible character.
\[Rho]
(Mathematica Character Name) Unicode: 03C1. Aliases: Esc r Esc, Esc rho Esc. Greek letter.
Unicode: 221F. Letter-like form. Used in geometry to indicate a right angle, as in the symbol ∟ ABC.
Unicode: 21E5. Infix arrow operator. x ⇥ y is by default interpreted as RightArrowBar[x,y]. Used in mathematics to indicate an epimorphism. Sometimes used to indicate a tab. ...
Unicode: 21C4. Infix arrow operator. x ⇄ y is by default interpreted as RightArrowLeftArrow[x,y]. Extensible character.
Unicode: 2309. Alias: Esc rc Esc. Matchfix operator with built-in evaluation rules. ⌈ x ⌉ is by default interpreted as Ceiling[x]. Extensible character.
Unicode: 301B. Alias: Esc ]] Esc. m 〚i,j,… 〛 is by default interpreted as Part[m,i,j,…]. Extensible character; grows by default to limited size.
Unicode: 295D. Infix arrow-like operator. x ⥝ y is by default interpreted as RightDownTeeVector[x,y]. Extensible character.