One of the most important convictions of the modern linguist is that every human language is a system which involves a great degree of complexity, far greater than we normally realize. It has also been established that what applies in the case of one language may not necessarily apply in another. In view of these facts and due to the nature of our study (in which various aspects of linguistic structure characteristic of more than one language are frequently discussed and compared) we have found it necessary to supply the reader with a clear idea of the fundamental principles of Arabic word structure. Another important purpose to be served by the present discussion consists in the realization that for our analysis of the various issues to be precise and scientific, it must employ a set of clearly defined concepts in accordance with which facts and claims can safely and confidently be stated.