“A measure of how easy it is to comprehend a text depending on a number of variables. These include vocabulary, sentence complexity, format, writing style, and topic, plus the reading comprehension level, interest, background information, and decoding skills of the reader.
Some methods of predicting the readability of a text are used to gauge whether an individual can successfully read and comprehend a passage. One such method is to read a section of a passage and count the number of words that are unfamiliar to the reader. If, for example, the reader encounters more than three unfamiliar words, the readability may be too difficult.
In educational settings, a text’s readability is often measured in grade level. For example, a history textbook with a readability of 9.3 means an average ninth grade, third month student should be able to read and comprehend it.”
Excerpted from: Turkington, Carol, and Joseph R. Harris, PhD. The Encyclopedia of Learning Disabilities. New York: Facts on File, 2006.