Five laws of library science
The Five laws of library science is a theory proposed by S. R. Ranganathan in 1931, detailing the principles of operating a library system. Many librarians worldwide accept them as the foundations of their philosophy.
These laws are:
- Books are for use.
- Every reader his [or her] book.
- Every book its reader.
- Save the time of the reader.
- The library is a growing organism.
First law: Books are for Use. 
The first law constitutes the basis for the library services. Ranganathan observed that books were often chained to prevent their removal and that the emphasis was on storage and preservation rather than use. He did not reject the notion that preservation and storage were important, but he asserted that the purpose of such activities was to promote the use of them. Without the use of materials, there is little value in the item. By emphasizing use, Ranganathan refocused the attention of the field to access-related issues, such as the library's location, loan policies, hours and days of operation, as well as such mundanities as library furniture and the quality of staffing.
Second Law: Every person his or her book 
This law suggests that every member of the community should be able to obtain materials needed. Ranganathan felt that all individuals from all social environments were entitled to library service, and that the basis of library use was education, to which all were entitled. These entitlements were not without some important obligations for both libraries/librarians and library patrons. Librarians should have excellent first-hand knowledge of the people to be served. Collections should meet the special interests of the community, and libraries should promote and advertise their services extensively to attract a wide range of readers. 
Third Law: Every book its reader 
This principle is closely related to the second law but it focuses on the item itself, suggesting that each item in a library has an individual or individuals who would find that item useful. Ranganathan argued that the library could devise many methods to ensure that each item finds it appropriate reader. One method involved the basic rules for access to the collection, most notably the need for open shelving.
Fourth Law: Save the time of the reader 
This law is a recognition that part of the excellence of library service is its ability to meet the needs of the library user efficiently. To this end, Ranganathan recommended the use of appropriate business methods to improve library management. He observed that centralizing the library collection in one location provided distinct advantages. He also noted that excellent staff would not only include those who possess strong reference skills, but also strong technical skills in cataloging, cross-referencing, ordering, accessioning, and the circulation of materials.
Fifth Law: The library is a growing organism 
This law focused more on the need for internal change than on changes in the environment itself. He argued that library organizations must accommodate growth in staff, the physical collection, and patron use. This involved allowing for growth in the physical building, reading areas, shelving, and in space for the catalog.
Librarian Michael Gorman (past president of the American Library Association, 2005–2006), and Walt Crawford recommended the following laws in addition to Ranganathan's five in Future Libraries: Dreams, Madness, and Realities [American Library Association, 1995], (p. 8) Gorman later repeated them in his small book, Our Singular Strengths [American Library Association, 1998].
- Libraries serve humanity.
- Respect all forms by which knowledge is communicated.
- Use technology intelligently to enhance service.
- Protect free access to knowledge.
- Honor the past and create the future.
In 2004, librarian Alireza Noruzi recommended applying Ranganathan's laws to the Web in his paper, "Application of Ranganathan's Laws to the Web":
- Web resources are for use.
- Every user has his or her web resource.
- Every web resource its user.
- Save the time of the user.
- The Web is a growing organism.
In 2008, librarian Carol Simpson recommended that editing be done to Ranganathan's law due to media richness. The following were:
- Media are for use.
- Every patron his information.
- Every medium its user.
- Save the time of the patron.
- The library is a growing organism.
- Koehler, Wallace, Jitka Hurych, Wanda Dole, and Joanna Wall. "Ethical Values of Information and Library Professionals – An Expanded Analysis." International Information & Library Review 32 (3/4) 2000: 485–506.
- Rubin, Richard E. Foundations of Library and Information Science. 2nd ed. New York: Neal-Schuman Publishers. 2004.
- Noruzi, Alireza (2004). "Application of Ranganathan's Laws to the Web." Webology, 1(2), Article 8. Available at: http://www.webology.org/2004/v1n2/a8.html
- Simpson, Carol. "Five Laws". Library Media Connection 26 no7 6 Ap/My 2008. Available at: http://www.carolsimpson.com/5laws.pdf
- Full text of The Five Laws of Library Science at HathiTrust Digital Library.