LaTeX Error: Command \foo already defined

TeX Output

./example.tex:2: LaTeX Error: Command \textbf already defined.
               Or name \end... illegal, see p.192 of the manual.
l.2 \newcommand{\textbf}
                        [1]{#1}

Explanation

The \newcommand macro creates a new command, but protects existing definitions by aborting if a command with that name already exists in LaTeX or a loaded package.

How to Fix

• If you intend to override the existing command, use \renewcommand:

  \renewcommand{\textbf}[1]{#1}
  

• If you intended to define a new unique macro, rename it:

  \newcommand{\mycustombold}[1]{#1}
  

• If the macro might or might not already exist depending on engine/packages, use \providecommand.