Over 60 percent of all English words have Greek or Latin roots. In the vocabulary of the sciences and technology, the figure rises to over 90 percent. About 10 percent of the Latin vocabulary has found its way directly into English without an intermediary (usually French).This handbook is designed to increase and consolidate the English vocabulary of Greco-Latin origin. It is divided into two practically equal sections, which present, respectively, the vocabulary of Latin origin and that of Greek origin.Each of these sections begins with a list of the main English roots derived from Latin or Greek. These roots, unlike other handbooks, are classified according to the order of Latin or Greek grammar. That is, they are presented by grammatical categories (nouns, adjectives, verbs, etc.). Within each grammatical category, the structure of Latin or Greek grammar is followed: name of the declension, type of verb, etc. Thanks to this, the reader can more easily grasp the similarity between English and Latin or Greek words.After this list of roots, there is a section of prefixes and suffixes of Latin or Greek origin. Affixes are a very important mechanism for building new words. In Latin and Greek, they were very productive, and English has inherited this productivity, which coexists with other mechanisms typical of its Germanic origin. Greco-Latin affixes are still alive and many new words being created use them.Finally, in the section on Greek etymologies, a chapter groups Greek and Latin terminology according to the semantic field. In this way, the reader can observe and practice the areas in which Latin and Greek have been most decisive: medicine, botany, social sciences, etc.In each of these sections, there are review and consolidation exercises. These exercises are intended to be varied and insist on the most important roots that should be thoroughly understood.Not all the words presented throughout the book are equally important. Some belong to the everyday lexicon, while others are only found in very specialized contexts. We have decided to present the maximum number of words, to understand the impact of the Greco-Latin influence, and to facilitate their memorization, by grouping all the words from the same root. The book has an answer key at the end.