ams
The ams extension implements AMS math environments and macros, and
macros for accessing the characters in the AMS symbol fonts. This
extension is already loaded in all the components that include
the TeX input jax, other than input/tex-base. See the list
of control sequences for details about what commands
are implemented in this extension.
To load the ams extension explicitly (when using
input/tex-base for example), add '[tex]/ams' to the
load array of the loader block of your MathJax configuration,
and add 'ams' to the packages array of the tex block.
window.MathJax = {
loader: {load: ['[tex]/ams']},
tex: {packages: {'[+]': ['ams']}}
};
Alternatively, use \require{ams} in a TeX expression to load it
dynamically from within the math on the page, if the require
extension is loaded.
Since the ams extension is included in the combined components that contain the TeX input jax, it will already be in the package list. In that case, if you want to disable it, you can remove it:
window.MathJax = {
tex: {packages: {'[-]': ['ams']}}
};