Translation is one of the main vectors for other civilization and cultures, and therefore finding a correct definition of translation and controlling the terminology of translation science, whose incorrect use lead to confusion among translation theorists. Of course, the correct definition and control of translation science terminology leads to an accurate understanding and correct application of the translation process. To draw a comprehensive agreed-upon definition to translation, the study goes through and assesses historic opinions and correct their possible faults. An astonishing paradox is that Arabs are the first to define translation since the translation proposed by Aljahez (800s AD), in his book of "The Animal" in a brief, but comprehensive, text covering a lot of translation issues. According to the researcher, this definition is the most accurate, even compared to more modern ones. Hence, the study launches with a critical analysis to the Translation definition both old and new. It, moreover, tries to develop a definition of translation of the presented ones, which is characterized by a consensus and serves the process of translation.