ISO 4 (Information and documentation – Rules for the abbreviation of title words and titles of publications) is an international standard, which defines a uniform system for the abbreviation of serial titles, i.e., titles of publications such as scientific journals that are published in regular installments. The ISSN International Centre, which the International Organization for Standardization (ISO) has appointed as the registration authority for ISO 4, maintains the "List of Title Word Abbreviations", which are standard abbreviations for words commonly found in serial titles.
One major use of ISO 4 is to abbreviate the names of scientific journals using the List of Title Word Abbreviations (LTWA). For instance, when citing a paper from the European Physical Journal, the ISO 4 standard prescribes "Eur. Phys. J." to be used as the abbreviation. ISO 4 is particularly efficient for abbreviating journal titles: for example, the letter "J." is the standard abbreviation for the word "journal".
- "Online services: Access to the LTWA". International Standard Serial Number International Centre. Retrieved 22 October 2014.