In an effort to get GNOME applications that support Plugins, Extensions,
Addins, etc., to have a consistent name, I propose using the name "Extensions"
[1].

From comment #18 on my blog post about the subject [1], I conclude:

  a) There seems to be complete agreement that Add-ins, Add-ons, or anything
that could be hyphenized is out of the question. Looks funny too.

  b) That pretty much leaves us with “Extensions” and “Plugins.”

  c) “Extensions” seems to be best suited for internationalization, and you
can’t really mess it up (I’d love to see someone spell it Exten-sions).
“Plugins” degrades across cultural boundaries [2]. That said, I don’t
think getting into a deep analysis of the vague differences between Extensions
and Plugins is necessary. For all intents and purposes, they convey the same
thing.

[1] http://abock.org/2007/11/14/plugins-addins-extensions-oh-my/
[2] The fact that "Plugins" is very hard to translate was brought up by a
number of people. "Extensions" apparently does not have this problem (comment
#8):

  "I vote for Extensions. In Italian you can’t really translate plugin, thus
one has got to let it untraslated. Every time I use the word “plugin” I
have to spend 5 min explaining it. So, besides being very culturally
insensitive, it’s time consuming as well."