This dictionary has been improved through the addition of English definitions, parallel to the existing French definitions, while all equivalencies have been reviewed in light of the most up-to-date sources. The terms are in alphabetical order according to the English key terms, and it includes a French-English glossary. The terms in the new dictionary remain essentially the same, with approximately 1,000 concepts and some 3,000 terminological units in the two official languages. It covers three sub-fields, namely physicochemical reactions involving ozone in the atmosphere, atmospheric layers, and the symptomatology of skin cancers caused by the sun's rays.