7 Essential Words of Fall
a software application in which advertisements are displayed while the program is running, esp. in pop-up windows or banners, and which often is installed without the user's knowledge or consent; also called advertising-supported software
a form of spyware that collects information about the computer user's online behavior in order to display targeted advertisements in the Web browser
Any kind of software which is distributed free of charge along with advertisements that are either placed on the web site from which the software is distributed or displayed by the program while it is running.
Nagware might be considered a special case of adware where the program tries to persuade the user to buy a license for the program itself.