The present volume comprises the contributions of some of the participants of the NATO Advance Studies Institute "Turbulence, Weak and Strong", held in Cargese, in August 1994. More than 70 scientists, from seniors to young students, have joined to­ gether to discuss and review new (and not so new) ideas and developments in the study of turbulence. One of the objectives of the School was to incorporate, in the same meeting, two aspects of turbulence, which are obviously linked, and which are often treated sep­ arately: fully developed turbulence (in two and three dimensions) and weak turbulence (essentially one and two-dimensional systems). The idea of preparing a dictionary rather than ordinary proceedings started from the feeling that the terminology of turbulence includes many long, technical, poorly evocative words, which are usually not understood by people exterior to the field, and which might be worth explaining. Students who start working in the field of turbulence face a sort of curious situation: on one side, they are aware that turbulence is related to the disordered, churning flows of torrents, the pow­ erful movements of water in the oceans, the violent jet streams in the troposphere, the solar eruptions, and they are certainly excited to pierce the mystery of this fascinating, omnipresent phenomenon.