1. A system for translation between source and target language comprising: input means for entering a key word in the source language and for selecting a subject category relating to the subject of the translation; first memory means for containing sentences in said source language, said source language sentences being arranged according to subject category; second memory means for containing sentences in said target language, said target language sentences being arranged in said second memory means with addresses corresponding to the addresses of the source language sentences in said first memory means having the same meaning; first addressing means responsive to said input means for selecting an address location in said first memory means corresponding to the beginning of the selected subject category; search means responsive to said input means and said first addressing means for searching said first memory means and comparing said entered key word to the words of the sentences within said selected subject category in said first memory means, said search means identifying a sentence containing said key word and its associated address; said first addressing means incrementing said address location by one after each comparison by said search means until said search means identifies said sentence containing said key word and its associated address; second addressing and retrieval means for accessing the target sentence located at the address in said second memory means corresponding to the address of the sentence in said first memory means containing the key word and retrieving said target sentence; and display means responsive to said second addressing and retrieval means for presenting said target sentence to the user of the system.