As I've started learning about lisp, emacs, and ess (Emacs Speaks Statistics), I've come across this concept of inferior-this-or-that. For instance, there's an inferior-ess-mode, inferior-lisp, and Inferior Emacs Lisp Mode.
In all these cases, it seems that some interpreted language is running within emacs, and you can interact with it within a buffer. But why are they inferior and what are they inferior to?
An inferior mode refers to a mode which run as a subprocess of emacs.
For example, this is my process tree when I start emacs:
$ pstree 62238 --= 62238 smt /usr/local/Cellar/emacs/HEAD/Emacs.app/Contents/MacOS/Emacs
After I run an inferior tcl shell, this is what my process tree looks like:
$ pstree 62238 -+= 62238 smt /usr/local/Cellar/emacs/HEAD/Emacs.app/Contents/MacOS/Emacs \-+= 62359 smt /bin/sh /usr/bin/wish \--- 62361 smt /usr/bin/../../System/Library/Frameworks/Tk.framework/Version
Another way of saying this might be that "inferior" is synonymous with the prefix "sub-" in this context.