Una persona, un grupo, un dispositivo o un proceso. [UNE-71504:2008]

An individual (person), organization, device or process. [NIST-SP800-57:2007]

a person, a group, a device or a process. [ISO-19790:2006]

Either a subject (an active element that operates on information or the system state) or an object (a passive element that contains or receives information). [NIST-SP800-27:2004]

Either a subject (an active element that operates on information or the system state) or an object (a passive element that contains or receives information). [NIST-SP800-33:2001]