Users can search this database of British rock units by rock unit, preferred map code, maximum age of rock unit, and database status code (described at site) and retrieve information about which British Geological Survey (BGS) maps and publications cover those units. For example, a search for Stockdale Group and Ashgil leads to a record citing the lithology, upper and lower boundary definitions, unit thickness, geographic extent, parent unit, previous name, stratotype, and bibliographic reference for the Paleozoic Stockdale Group of Northern England. The Lexicon is intended foremost as a reference source and dictionary for the use of BGS geoscientists, but the basic information on the stratigraphical framework and rock terminology of the UK is useful for non-BGS geologists visiting the site.