   ("increment" . ("∆"))
   ("inf"       . ("∞"))
   ("&"         . ("⅋"))
+  ("op"        . ("ᵒᵖ"))
 
   ;; Circled operators.
 

  ("en"         . ("–"))
  ("em"         . ("—"))
  ("^i"         . ("ⁱ"))
  ("!!"         . ("‼"))
  ("??"         . ("⁇"))
  ("?!"         . ("‽" "⁈"))

  ;; Various operators/symbols.
  ("tr"        . ("⬝"))
  ("sy"        . ("⁻¹"))
  ("inv"       . ("⁻¹"))
  ("-1"       . ("⁻¹"))
  ("qed"       . ("∎"))
  ("x"         . ("×"))
  ("o"         . ("∘"))
