1. A machine translation system comprising: (a) a machine translation module for performing machine translation of an input text in a source language to an output text in a target language using a dictionary database containing entries for words of the target language corresponding to words of the source language; (b) a dictionary database including a core language dictionary containing entries for generic words of a source/target language pair, a plurality of sublanguage dictionaries each containing entries for specialized words of a respective one of a plurality of sublanguages handled by the machine translation system for the source/target language pair, and a plurality of user dictionaries each containing entries for individualized words used by a respective one of a plurality of users of the machine translation system for the source/target language pair; (c) a receiving interface for receiving a particular input text sent by a particular user and accompanying control inputs indicative of a preferred sublanguage applicable to the particular input text out of a plurality of possible sublanguages and indicative of a preferred user dictionary out of the plurality of user dictionaries; and (d) a dictionary control module responsive to the control inputs received by the receiving interface for causing the machine translation module to use the core language dictionary, and for selecting a preferred sublanguage dictionary and a preferred user dictionary for use by the machine translation module for translation of the input text, wherein said receiving interface further includes a programmed module for allowing users of the machine translation system to input scratch entries for individualized words into their respective user dictionaries, and wherein said dictionary control module further includes an automated dictionary maintenance utility for automatically assessing whether a word entry has been entered as a scratch word entry in common to a given number or grouping of users through their respective user dictionaries and for thereupon automatically entering said word entry into a higher-level sublanguage dictionary for a sublanguage encompassing those users.