Difference between \providecommand and \newcommand in LaTeX

These two commands are similar but have one important difference:

• \newcommand: Defines a new command. If the command already exists, LaTeX will produce an error.
• \providecommand: Also defines a new command, but if the command already exists, LaTeX will silently ignore the new definition and keep the existing one.

Example usage:

\newcommand{\mycommand}{This is my command}
% If \mycommand is already defined, this will give an error

\providecommand{\myothercommand}{This is my other command}
% If \myothercommand is already defined, this will be ignored silently

When to use which:

• Use \newcommand when you want to be warned if you’re accidentally redefining an existing command
• Use \providecommand when you’re writing a package or document that needs to work seamlessly without overriding existing definitions

The \providecommand command is particularly useful in package development to offer default definitions that can be overridden by the user.

Here are some tags that could be generated from the note [[Latex Tips]]:

• #latex/commands
• #latex/newcommand
• #latex/providecommand
• #latex/definitions
• #latex/package-development