PageRank is a link analysis algorithm used by the Google Internet search engine that assigns a numerical weighting to each element of a hyperlinked set of documents, such as the World Wide Web, with the purpose of "measuring" its relative importance within the set. Google assigns a numeric weighting from 0-10 for each webpage on the Internet; this PageRank? denotes a site’s importance in the eyes of Google.

The PageRank? is derived from a theoretical probability value on a logarithmic scale like the Richter Scale. The PageRank? of a particular page is roughly based upon the quantity of inbound links as well as the PageRank? of the pages providing the links. The algorithm may be applied to any collection of entities with reciprocal quotations and references. The numerical weight that it assigns to any given element E is also called the PageRank? of E and denoted by PR(E).

It is known that other factors, e.g. relevance of search words on the page and actual visits to the page reported by the Google toolbar also influence the PageRank?. Other link-based ranking algorithms for Web pages include the HITS algorithm invented by Jon Kleinberg (used by Teoma and now Ask.com), the IBM CLEVER project, and the TrustRank? algorithm.