The cause of writing this book was the author’s wish to give students of the Aegean University and students of other Greek Universities the opportunity to familiarize themselves by the means of a short manual with the fundamental concepts of International Law and to teach them the corresponding English language and terminology, as English language dominates in international relations and international law. Many books, treatises, monographs and articles in the field of international law have been written in English. Therefore, studying thoroughly international law English terminology is a necessary condition for the expansion of knowledge in this branch of law. For this reason the author left intact English wordings found in various legal works which he used. One could characterize this handbook as an Introduction to International Law. However, the author believes that any Introduction should, in order to achieve its aim, have both clear wordings and primarily a certain form in the presentation of chapters. The aim of this book is to help students learn the absolutely necessary notions and principles of international law in a short time and enable them to understand juridical treatises of international law.