31.2 Top-Level Definitions, or Defuns

In Emacs, a major definition at the top level in the buffer, something like a function, is called a defun. The name comes from Lisp, but in Emacs we use it for all languages.

In many programming language modes, Emacs assumes that a defun is any pair of parentheses (or braces, if the language uses braces this way) that starts at the left margin. For example, in C, the body of a function definition is a defun, usually recognized as an open-brace that begins at the left margin¹. A variable's initializer can also count as a defun, if the open-brace that begins the initializer is at the left margin.

However, some language modes provide their own code for recognizing defuns in a way that suits the language syntax and conventions better.

• Left Margin Paren: An open-paren or similar opening delimiter starts a defun if it is at the left margin.
• Moving by Defuns: Commands to move over or mark a major definition.
• Imenu: Making buffer indexes as menus.
• Which Function: Which Function mode shows which function you are in.