Based on the logMAR principle, All charts have ten words per print size: two each of 4-letter, 5-letter, 6-letter, 7-letter and 8-letter words. The words are selected from a list of the 5000 most common words in American English according to www.wordfrequency.info and the 4000 most common Spanish words and expressions according to www.learningspanish-spain.com