Stickiness
The average minutes per month visitors spend at a site or network.
A sticky Web site is one which attracts many return visitors. Sometimes stickiness is measured in terms of page views. When defined as minutes per month, site stickiness is a function of number of visits (repeat usage) and time spent per visit (session stickiness).
High-quality fresh content is the key to making a Web site sticky, a goal of good Web site design.