Additions to programs to increase their functionality. On the Internet, this usually refers to plugins for browsers. The most popular include Apple's Quicktime video player, Real Networks RealPlayer for its streaming media format and Macromedia's Shockwave player for its Flash animation.

a loadable piece of software - a dll in windowsland, or a bundle in MacOsX - that adds functionality to an existing program

Are small programs that add extra features to your web browser. They can usually be downloaded for free.

NOMOS uses a variety of plugins to display, process, and interact with data. Plugins are Java code extensions to the NOMOS code base. NOMOS allows for the usage and development of several different types of plugins: tracks, labels, panels, scripts. NOMOS provides a full-featured annotation environment out-of-the-box, but it may be useful to create custom-designed interfaces for specific annotation tasks. For these tasks, new or derived plugins provide a mechanism for altering NOMOS's default behavior.

Small, task-oriented function that intercepts content before it is displayed and manipulates it in some way. Joomla! provides a number of Plugins in the core distribution, such as WYSIWYG editors, 3rd party component and module searchers, etc.