Citizen science is a term used for a project or ongoing program of scientific work in which a network of volunteers, many of whom may have no specific scientific training, perform or manage research-related tasks such as observation, measurement or computation.
The use of such networks often allows scientists to accomplish research objectives more feasibly than would otherwise be possible. In addition, these projects aim to promote public engagement with the research, as well as with science in general. Some programs provide materials specifically for use by primary or secondary school students. As such, citizen science is one approach to informal science education.
The longest-running currently active citizen science project is probably the Audubon Society's Christmas Bird Count, which started in 1900. Other well-known examples of citizen science programs include World Water Monitoring Day, NASA's Stardust@home and Clickworkers, and a variety of projects run by the Cornell Laboratory of Ornithology. Distributed computing ventures such as SETI@home may also be considered citizen science, even though the primary task of computation is performed by volunteers' computers.
Bruce Lewenstein of Cornell University's Communication and S&TS departments points out two additional usages of the terms "citizen science" and "citizen scientist:"