In Writing

Readability is defined as reading ease, especially as it results from a writing style. Extensive research has shown that easy-reading text improves comprehension, retention, reading speed, and reading persistence.

Ease-of-reading is the result of the interaction between the text and the reader. In the reader, those features affecting readability are 1. prior knowledge, 2. reading skill, 3. interest, and 4. motivation. In the text, those features are 1. content, 2. style, 3. design, and 4. structure^[1]. The design can include the medium, layout, illustrations, reading and navigation aids, typeface, and color.

Among language experts, readability is a score produced by a readability formula. The formulas are widely used to match texts with the reading level of the audience. Extensive research has shown that the popular readability formulas are not 100% accurate, but they give a "good rough estimate" of the reading skill required to read a text. The readability formulas have greatly benefited millions of readers throughout the world in many languages. If there is any problem with the formulas, it is that they are not used enough ^{[2] [3] [4]}.

Publishers not only use readability formulas to assess the reading level of a text. They also use word-frequency lists. The frequency of a word is a good indication of its ease-of-use. Text leveling, a subjective evaluation of a text based on training and experience, is another important adjunct of using a formula^[5].

Since the 1930s, national literacy surveys have shown that the average adult in the U.S. reads at the 8th-grade level. It is important to remember that one's level of education is no indication of one's reading skill. Many high-school graduates read at the 8th-grade level, college graduates at the 10th-grade level. With practice, readers with little formal education can often become advanced readers. (DuBay 2006, National Assessment of Adult Literacy).

Nearly all of today's blockbuster writers write at the 7th-grade level, including John Grisham, Stephen King, J. K. Rowling, and Dan Brown. Experts today recommend writing legal and health information at the 7th-grade level. Laws often require writing medical and safety information at the 5th-grade level^[6]. Learning to write for a class of readers other than one's own is very difficult. It takes method, training, and lots of practice. As Jacques Barzun wrote, "Simple English is no person's native tongue."

Readability may be assessed by conducting a readability survey or by application of readability tests, which have been established through analysis of readability survey results. Writers, editors, and publishers often make intuitive assessments of readability based on experience, insight into their target audience, and knowledge of a number of rules of thumb (e.g., English textbooks are most readable when laid out with 20% whitespace on the page), which are often derived from assessing a number of readability survey results.

Re-readability - the propensity to read something again after a period of time - appears to be a criterion dependent upon the reader. However, some authors, such as Robert A. Heinlein, appear more able to produce re-readable works, as is apparent from the rate of re-printing.

Common measures of readability of text

In alphabetical order, with no implications about which is most useful or most often used:

• Automated Readability Index
• Coleman-Liau
• Flesch Reading Ease^[7]
• Flesch?Kincaid Grade Level. This uses use the same core measures as Flesch Reading Ease (word length and sentence length). But the two measures have different weighting factors, so the results of the two tests do not always correlate: if one analyzes two texts using both measures, one text may get a more favorable score on the Reading Ease test and the other may get the better score on the Grade Level test.
• SMOG
• Gunning Fog

There are many computer programs for measuring the readability of text. Some are available via Websites, and some of these are specifically designed to measure the readability of Web pages.

In Computer Programming

In computer programming, readability refers to the ease with which a human reader can comprehend the purpose, control flow, and operation of source code.

Readability is important because programmers spend the majority of their time reading, trying to understand and modifying existing source code, rather than writing new source code. Unreadable code often leads to bugs, inefficiencies, and duplicated code. A study^[8] found that a few simple readability transformations made code shorter and drastically reduced the time to understand it.

Following a consistent programming style often helps readability. However, readability is more than just programming style. Many factors, having little or nothing to do with the ability of the computer to efficiently compile and execute the code, contribute to readability. Some of these factors include:

• Different indentation styles (whitespace)
• Comments
• Decomposition
• Naming conventions for objects (such as variables, classes, procedures, etc)

In typography

Correct use of type size, line spacing, column width, text-color-background contrast and white space make text easy to read. See Typography for more details.

References

1. ↑ Gray, W. S. and B. Leary. 1935. What makes a book readable. Chicago: Chicago University Press.
2. ↑ Chall, J. S. 1958. Readability: An appraisal of research and application. Columbus, OH:Ohio State University Press.
3. ↑ DuBay, W. H. 2006. Smart language: Readers, Readability, and the Grading of Text. Costa Mesa:Impact Information.
4. ↑ Klare, G. R. 1963. The measurement of readability. T. Ames, IA:Iowa State University Press.
5. ↑ Fry, E. 2002. "Readability versus leveling." Reading teacher 56, no. 3:286-292.
6. ↑ Doak, C. C., L. G. Doak, and J. H. Root. 1996. Teaching patients with low literacy skills. Philadelphia: J. P. Lippincott Company.
   • DuBay, W. H. 2004. ''The Principles of Readability''.
7. ↑ Flesch, R. 1946. The art of plain talk. New York:Harpers.
8. ↑ James L. Elshoff , Michael Marcotty, Improving computer program readability to aid modification, Communications of the ACM, v.25 n.8, p.512-521, Aug 1982.