SiS

SIS most commonly refers to the United Kingdom's Secret Intelligence Service, the British foreign intelligence agency responsible for gathering intelligence overseas, conducting covert operations, and counterintelligence. Publicly known by its code name MI6, the service operates under the Foreign, Commonwealth & Development Office and has roots dating to the early 20th century.

In academia, SIS is the abbreviation for the School of International Service at American University in Washington, D.C. This academic unit offers undergraduate and graduate programs focused on international relations, global politics, and related fields, and is a prominent hub for international affairs education in the United States.

In information technology and administration, SIS stands for Student Information System, a software platform used by educational institutions to store and manage student records, enrollment, attendance, grades, and other administrative data. These systems facilitate course registration, scheduling, reporting, and compliance with regulatory requirements.

Other uses of the acronym exist across different sectors, including governmental, corporate, and professional contexts, where SIS may denote specific organizations, systems, or programs. Because SIS is an acronym with multiple, context-dependent meanings, its intended interpretation depends on the surrounding information and field of reference.