A plugin is a piece of software containing a group of functions that can be added to a WordPress website.
http://simonrclo568.institutoalvorada.org/a-plugin-is-a-piece-of-software-application-consisting-of-a-group-of-functions-that-can-be-added-to-a-wordpress-website
A plugin is a piece of software application including a group of functions that can be added to a WordPress site.