1. A machine translation system for translating a first language into a second language, which comprises: input means for entry of an original written sentence in the first language into the system; dictionary means having at least a first dictionary for storing various words in various parts of speech and their translation in the second language respectively corresponding to the words in the first language, and a second dictionary for storing various words designated as nouns corresponding to words in the first language; translation means for analyzing the original written sentence in the first language, for retrieving said dictionary means and for executing the translation processing of the input original, when any same word designated as nouns stored in the first dictionary is found in the second dictionary, the word stored in the second dictionary takes precedence over that in the first dictionary in the translation means; and output means for producing translated sentences in the second language obtained from said translation means.