Google defined the lower case knol as a "unit of knowledge", which is referring to an article in the project. Several experts saw Knol as Google's attempt to compete with Wikipedia as others pointed out the differences between them.
On January 16, 2009, Google announced that Knol had grown to over 100,000 articles, and users from 197 countries visited Knol on average. Since then, the Public Library of Science Currents Influenz and the Harvard University-sponsored forum for Healthcare Information Technology (HIT) Platform have utilized Knol-based collections for rapid exchange of research.
On the website, they've given a final message about it's stopping point.
Knol has been discontinued as of May 1, 2012
Knol has been discontinued as a service, but we've worked with Solvitor and Crowd Favorite to create Annotum, an open-source platform based upon WordPress that allows you to continue authoring and publishing scholarly articles. To learn more about this announcement, see our Frequently Asked Questions.