By the Project For Excellence In Journalism
Circulation: The average number of copies of a newspaper distributed or sold in a given time period. Often expressed as daily circulation (Monday-Saturday) or Sunday circulation.
Pay wall: A policy of limiting access to a website (or a part of a website) to users who pay a fee or purchase a subcription.
Media fragmentation: Increased channels for disseminating information (e.g. newspapers, cable television, Web sites, etc.)