Package texlive-etex

An extended version of TeX, from the NTS project

An extended version of TeX (which is capable of running as if
it were TeX unmodified). E-TeX has been specified by the LaTeX
team as the engine for the development of LaTeX 2e, in the
immediate future; as a result, LaTeX programmers may (in all
current TeX distributions) assume e-TeX functionality.
Development versions of e-TeX are to be found in the TeX live
source repository.

General Commands
Command Description
etex extended (plain) TeX