The aim of this paper is to review some of the findings in the field of readability research. First, the differences in meaning between the terms ‘readability’ and ‘legibility’ are discussed. Next, the origins and developments of readability formulas are examined in detail. Then, the best‐known formulas for English language material are described so as to give the reader a brief overview of what has been achieved in this field of research. Finally, the principal applications of these formulas are described.