From the site: "WordCount is an artistic experiment in the way we use language. It presents the 86,800 most frequently used English words, ranked in order of commonness. Each word is scaled to reflect its frequency relative to the words that precede and follow it, giving a visual barometer of relevance. The larger the word, the more we use it. The smaller the word, the more uncommon it is."
Also don't miss: "NEW! WordCount tracks the way we use language. QueryCount tracks the way we use WordCount."