Katrien Depuydt of the Institute for Dutch Lexicology (INL) begins with the distinction between a lexicon and an electronic dictionary. Dictionaries are primarily for human use and organised so that each entry is an item in itself. Lexica on the other hand are primarily for computation, and used for linguistic annotation, enhanced retrieval (like tracking inflected forms of words), and for syntactic parsing and machine retrieval. Where a dictionary gives you the history of words; lexica give you the history of a language.