Extensive reading is a way of learning a language, especially a second or foreign language.
First language and second language [change]
Free voluntary reading is one name for extensive reading in first language education. Learners can choose a book that they like and to read it quickly or slowly. A free voluntary reading program is to help students to enjoy reading, so there are often no grades. In some schools this approach is also called Drop Everything and Read (DEAR).
In 1988, Day and Bamford described extensive reading for learning a second or foreign language. Students read as much as possible. Reading materials should use simple grammar and vocabulary so learners feel comfortable. Learners should read many different kinds of writing about different subjects. 
Graded Readers [change]
Many extensive reading programs use special series of books. These books use simplified grammar and vocabulary. They may be original stories, but many are shorter, easier versions of classic books.
Many teachers and some learners believe that extensive reading alone is enough to improve vocabulary. McQuillan and Krashen also believe this.However, other researchers say that extensive reading alone is not enough. Cobb and Parry have done research to show that there is a limit. Extensive reading may not improve vocabulary as much as people thought, especially for less common words.
- Day, R.; Bamford, J. (1988), Extensive Reading in the Second Language Classroom, Cambridge, U.K: Cambridge University Press
- Krashen, S. (1989), "We Acquire Vocabulary and Spelling by Reading: Additional Evidence for the Input Hypothesis", The Modern Language Journal, 73, pp. 440–464, http://www.jstor.org/stable/326879
- McQuillan, J.; Krashen, S.D. (2008), "Commentary: Can free reading take you all the way? A response to Cobb (2007)", About Language Learning & Technology, 6, pp. 104–109, http://llt.msu.edu/vol12num1/mcquillan/default.html
- Cobb, T. (2007), "Computing the Vocabulary Demands of L2 Reading", Language Learning & Technology, 11, pp. 38–63, http://llt.msu.edu/vol11num3/cobb/default.html
- Cobb, T. (2008), "Commentary: Response to McQuillan and Krashen (2008) [Can free reading take you all the way? A response to Cobb (2007)"], About Language Learning & Technology, 6, pp. 109–114, http://llt.msu.edu/vol12num1/cobb/default.html