Horace G. Danner’s A Thesaurus of English Word Roots is a compendium of the most-used word roots of the English language. As Timothy B. Noone notes in his foreword: “Dr. Danner’s book allows you not only to build up your passive English vocabulary, resulting in word recognition knowledge, but also gives you the rudiments for developing your active English vocabulary, making it possible to infer the meaning of words with which you are not yet acquainted. Your knowledge can now expand and will do so exponentially as your awareness of the roots in English words and your corresponding ability to decode unfamiliar words grows apace. This is the beginning of a fine mental linguistic library: so enjoy!” In A Thesaurus of English Word Roots, all word roots are listed alphabetically, along with the Greek or Latin words from which they derive, together with the roots’ original meanings. If the current meaning of an individual root differs from the original meaning, that is listed in a separate column. In the examples column, the words which contain the root are then listed, starting with their prefixes, for example, dysacousia, hyperacousia. These root-starting terms then are followed by terms where the root falls behind the word, e.g., acouesthesia and acoumeter. These words are followed by words where the root falls in the middle or the end, as in such terms as bradyacusia and odynacusis.. In this manner, A Thesaurus of English Word Roots places the word in as many word families as there are elements in the word. This work will interest linguists and philologists and anyone interested in the etymological aspects of English language.