This chapter discusses the concept of electronic dictionaries for humans following mainly De Schryver's definition. The technical medium gives a shape to a dictionary and can be paper or electronic. The medium largely affects the presentation and retrieval of lexicographic data. The advent of electronic dictionaries on CDs, whose content mirrored that of their paper counterparts, goes back to the 1980s. In Great Britain, the Collins English Dictionary is most likely to be the first dictionary brought out in the electronic format, initially on floppy discs, and then on CD. Electronic dictionaries have largely reduced search-related lexicographic costs, which are connected with dictionary consultation. Electronic dictionaries come in various shapes and sizes, from those book-like to those which are truly advanced and interactive. The most obvious advantage of the electronic medium manifests itself in simplified access structures, which make the electronic dictionary look-up time-effective and accurate.