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

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

  ("increment" . ("∆"))
  ("inf"       . ("∞"))
  ("&"         . ("⅋"))
  ("op"        . ("ᵒᵖ"))

  ;; Circled operators.

