.. _tex-newcommand:

##########
newcommand
##########

The `newcommand` extension provides the ``\def``, ``\newcommand``,
``\renewcommand``, ``\let``, ``\newenvironment``, and
``\renewenvironment`` macros for creating new macros and environments
in TeX.  For example,

.. code-block:: latex

    \(
       \def\RR{{\bf R}}
       \def\bold#1{{\bf #1}}
    \)

defines a macro ``\RR`` that produces a bold "R", while
``\bold{math}`` typesets its argument using a bold font.  See
:ref:`tex-macros` for more information.

This extension is already loaded in all the components that
include the TeX input jax, other than ``input/tex-base``.  To load the
`newcommand` extension explicitly (when using ``input/tex-base`` for
example), add ``'[tex]/newcommand'`` to the ``load`` array of the
``loader`` block of your MathJax configuration, and add
``'newcommand'`` to the ``packages`` array of the ``tex`` block.

.. code-block:: javascript

   window.MathJax = {
     loader: {load: ['[tex]/newcommand']},
     tex: {packages: {'[+]': ['newcommand']}}
   };

Alternatively, use ``\require{newcommand}`` in a TeX expression to load it
dynamically from within the math on the page, if the `require`
package is loaded.

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