Randfish, a new moderator at SEO Chat, has been discussing the Wordnet lexical database and how it can help SEOs. The actual history and information is at the advanced level, but Randfish does an excellent job of bringing the basics down to a level that I can at least understand. Since it is better documented in the forum thread here, I will let you read it for yourself. But the gist of it is that by using the Wordnet tool at www.cogsci.princeton.edu/cgi-bin/webwn, you are better equipped to handle Keyword Research, On-Topic Site Architecture, and On-Topic Links. So, head on off to both the tool and the thread and see how it can help you in your SEO efforts.
Using Wordnet for keyword research and more
