Cyc (pronounced /ˈsaɪk/ SYKE) is a long-term artificial intelligence project that aims to assemble a comprehensive ontology and knowledge base that spans the basic concepts and rules about how the world works.

For the latter, Cyc used a community-of-agents architecture in which specialized modules, each with its own algorithm, became prioritized if they could make progress on the sub-problem.

Cycorp stated its intention to release OpenCyc under parallel, unrestricted licences to meet the needs of its users.

The CycL and SubL interpreter (the program that allows users to browse and edit the database as well as to draw inferences) was released free of charge, but only as a binary, without source code.

[14] In July 2006, Cycorp released the executable of ResearchCyc 1.0, a version of Cyc aimed at the research community, at no charge.

[15] In 2007, the Cleveland Clinic has used Cyc to develop a natural-language query interface of biomedical information on cardiothoracic surgeries.

[20] CycSecure was produced in 2002,[21] a network vulnerability assessment tool based on Cyc, with trials at the US STRATCOM Computer Emergency Response Team.

[23] The application, called MathCraft,[24] was supposed to play the role of a fellow student who is slightly more confused than the user about the subject.

[25] Catherine Havasi, CEO of Luminoso, says that Cyc is the predecessor project to IBM's Watson.

[26] Machine-learning scientist Pedro Domingos refers to the project as a "catastrophic failure" for the unending amount of data required to produce any viable results and the inability for Cyc to evolve on its own.

[27] Gary Marcus, a cognitive scientist and the cofounder of an AI company called Geometric Intelligence, says "it represents an approach that is very different from all the deep-learning stuff that has been in the news.