"The ability to selectively control who can get at or manipulate information in, for example, a Web server." (Tim Berners-Lee, "Weaving the Web", 1999)
"The methods by which interactions with resources are limited to collections of users or programs for the purpose of enforcing integrity, confidentiality, or availability constraints." (Kim Haase et al, "The J2EE™ Tutorial", 2002)
"Limiting access to resources according to rights granted by the system administrator, application, or policy." (Tom Petrocelli, "Data Protection and Information Lifecycle Management", 2005)
"Determining who or what can go where, when, and how." (Judith Hurwitz et al, "Service Oriented Architecture For Dummies" 2nd Ed., 2009)
"Management of who is allowed access and who is not allowed access to networks, data files, applications, or other digital resources." (Linda Volonino & Efraim Turban, "Information Technology for Management" 8th Ed, 2011)
"Any mechanism to regulate access to something, but for parallel programs this term generally applies to shared memory. The term is sometimes extended to I/O devices as well. For parallel programming, the objective is generally to provide deterministic results by preventing an object from being modified by multiple tasks simultaneously. Most often this is referred to as mutual exclusion, which includes locks, mutexes, atomic operations, and transactional memory models. This may also require some control on reading access to prevent viewing of an object in a partially modified state." (Michael McCool et al, "Structured Parallel Programming", 2012)
"Secures content and identifies who can read, create, modify, and delete content." (Charles Cooper & Ann Rockley, "Managing Enterprise Content: A Unified Content Strategy" 2nd Ed., 2012)
"A technique used to permit or deny use of data or information system resources to specific users, programs, processes, or other systems based on previously granted authorization to those resources." (Mark Rhodes-Ousley, "Information Security: The Complete Reference, Second Edition" 2nd Ed., 2013)
"The act of limiting access to information system resources only to authorized users, programs, processes, or other systems." (Manish Agrawal, "Information Security and IT Risk Management", 2014)
"The means to ensure that access to assets is authorised and restricted on business and security requirements." (David Sutton, "Information Risk Management: A practitioner’s guide", 2014)
"Are security features that control how users and systems communicate and interact with other systems and resources." (Adam Gordon, "Official (ISC)2 Guide to the CISSP CBK" 4th Ed., 2015)
"Mechanisms, controls, and methods of limiting access to resources to authorized subjects only." (Shon Harris & Fernando Maymi, "CISSP All-in-One Exam Guide" 8th Ed, 2018)
"The process of granting or denying specific requests (1) for accessing and using information and related information processing services and (2) to enter specific physical facilities. Access control ensures that access to assets is authorized and restricted based on business and security requirements." (William Stallings, "Effective Cybersecurity: A Guide to Using Best Practices and Standards", 2018)