លេខសៀវភៅបទដ្ឋានអន្តរជាតិ (អង់គ្លេស៖ International Standard Book Number, អក្សរកាត់ ISBN) is a unique   numeric commercial book identifier based upon the 9-digit Standard Book Numbering (SBN) code created by Gordon Foster, Emeritus Professor of Statistics at Trinity College, Dublin,  for the booksellers and stationers W. H. Smith and others in 1965. 
The 10-digit ISBN format was developed by the International Organization for Standardization (ISO) and was published in 1970 as international standard ISO 2108.  (However, the 9-digit SBN code was used in the United Kingdom until 1974.) An SBN may be converted to an ISBN by prepending the digit "0". ISO has appointed the International ISBN Agency as the registration authority for ISBN worldwide and the ISBN Standard is developed under the control of ISO Technical Committee 46/Subcommittee 9 TC 46/SC 9. The ISO on-line facility only refers back to 1978. 
Since 1 January 2007, ISBNs have contained 13 digits, a format that is compatible with Bookland EAN-13s. 
Occasionally, a book may appear without a printed ISBN if it is printed privately or the author does not follow the usual ISBN procedure; however, this can be rectified later. 
Another identifier, the International Standard Serial Number (ISSN), identifies periodical publications such as magazines.
An ISBN is assigned to each edition and variation (except reprintings) of a book, for example an ebook, a paperback, and a hardcover would each have a different ISBN.  The ISBN is 13 digits long if assigned after January 1, 2007, and 10 digits long if assigned before 2007. An International Standard Book Number consists of 4 parts (if it is a 10 digit ISBN) or 5 parts (for a 13 digit ISBN):
The 13 digit ISBN separates its parts (prefix element, registration group, registrant, publication and check digit) with either a hyphen or a space. Other than the prefix element and the check digit, no part of the ISBN has a fixed number of digits.
The 10 digit ISBN also separated its parts (registration group, registrant, publication and check digit) with either a hyphen or a space. 
International Standard Book Numbers issuance is country-specific, in that ISBNs are issued by the ISBN registration agency that is responsible for that country or territory. The ranges of ISBNs assigned to any particular country are based on the publishing profile of the country concerned - e.g. the number of books and the number, type and size of publishers that are active. Some ISBN registration agencies are based in National Libraries or within Ministries of Culture and thus may receive direct funding from government to support their services. In other cases the ISBN registration service is provided by organisations such as bibliographic data providers who are not government funded. In Canada the stated purpose of issuing International Standard Book Numbers for no cost was to encourage Canadian culture. In the United Kingdom, United States, and some other countries, where the service is provided by non-government funded organisations the issuing of International Standard Book Numbers is a chargeable service.
Australia: In Australia ISBNs are issued by the commercial library services agency Thorpe-Bowker, and prices range from $40 for a single ISBN (plus a $55 registration fee for new publishers) through to $2,750 for a block of 1,000 ISBNs. 
Canada: In Canada Library and Archives Canada, a government agency, is the responsible entity, and there is no cost.
Pakistan: National Library of Pakistan  is responsible for ISBN registrations for Pakistani Publishers, Authors, Universities, Institutions and Government Departments who are responsible for publishing books.
United Kingdom and Ireland: In the United Kingdom and Ireland the privately held company, Nielsen Book Services, part of Nielsen Holdings N.V., is the responsible entity, and there is a charge. ISBNs are sold in lots of ten or more.
United States: In the United States the privately held company R. R. Bowker is the responsible entity, and there is a charge, which varies depending upon the number of ISBNs purchased, with prices ranging from $125.00 for a single number. 
Publishers and authors in other countries need to obtain ISBNs from their respective national ISBN registration Agency. A directory of ISBN Agencies is available on the International ISBN Agency website.
registration group identifier is a 1 to 5 digit number. The single digit group identifiers are: 0 or 1 for
The original standard book number (SBN) had no registration group identifier, but affixing a zero (0) as prefix to a 9-digit SBN creates a valid 10-digit ISBN.
The national ISBN agency assigns the registrant element ( cf. Category:ISBN agencies) and an accompanying series of ISBNs within that registrant element to the publisher; the publisher then allocates one of the ISBNs to each of his books. Generally, in most countries a book publisher is not required by law to assign an ISBN, however, most book stores only handle ISBN-bearing merchandise.
A listing of more than 900,000 assigned publisher codes is published, and can be ordered in book form ( €1399, US$1959). The web site of the ISBN agency does not offer any free method of looking up publisher codes.  Partial lists have been compiled (from library catalogs) for the English-language groups: identifier 0 and identifier 1.
Publishers receive blocks of ISBNs, with larger blocks allotted to publishers expecting to need them; a small publisher may receive ISBNs of one or more digits for the registration group identifier, several digits for the registrant, and a single digit for the publication element. Once that block of ISBNs is used, the publisher may receive another block of ISBNs, with a different registrant element. Consequently, a publisher may have different allotted registrant elements. There also may be more than one registration group identifier used in a country. This might occur once all the registrant elements from a particular registration group have been allocated to publishers.
By using variable block lengths, registration agencies are able to customise the allocations of ISBNs that they make to publishers. For example, a large publisher may be given a block of ISBNs where the digits allocated for the registrant element are few and there are many digits allocated for the publication element; likewise countries publishing a large output of titles have few allocated digits for the registration group identifier, and many for the registrant and publication elements.  Here are some sample ISBN-10 codes, illustrating block length variations.
|លេខ ISBN||ប្រទេស ឬតំបន់||គ្រឹះស្ថានបោះពុម្ពផ្សាយ|
|80-902734-1-6||Czech Republic; Slovakia||Taita Publishers|
|85-359-0277-5||ប្រេសុីល||Companhia das Letras|
|1-84356-028-3||English-speaking area||Simon Wallenberg Press|
|0-8044-2957-X||English-speaking area||Frederick Ungar|
|0-85131-041-9||English-speaking area||J. A. Allen & Co.|
|0-9752298-0-X||English-speaking area||KT Publishing|
English-language publisher codes follow a systematic pattern, which allows their length to be easily determined, as follows: 
|Item number length||0- group identifier||1- group identifier||Total|