1. An electronic dictionary for electronic translation of words or compound words in a source language at locations on a source medium, to corresponding words or compound words in a target language, the electronic dictionary comprising: a housing; an optical reader fixedly mounted in said housing so as to be fixed relative thereto, which optically reads from the source medium the source language to be translated; a translation unit which produces, on the basis of data output from the optical reader, an output in target language, corresponding to the source language; and means, including a printer fixedly mounted in said housing so as to be fixed relative to said housing and said optical reader, for automatically printing the target language produced by the translation unit at a fixed position on said source medium relative to the location on the source medium of the source language corresponding to the target language to be printed.