Etymology is the study of word origins and development. It provides one of the easiest and most effective ways to build vocabulary, because knowledge of some common roots and prefixes makes possible the figuring out of new word meanings. English is compounded of several languages, primarily Anglo-Saxon (Germanic) and Latin. Their Latin influence persists notably in the names of English cities ending in "-caster" or "-chester," from the Latin "castra" meaning "encampment." This is the fourth book of a series that focuses on etymology from Latin and Greek. This book focuses on Greek roots. The texts are designed to aid in learning the definitions of specific, deconstructed words. The meanings of a series of "reusable" classical prefixes and roots are presented that facilitate the deciphering of multiple related words.