Management
Management (or managing) is the administration of an organization, whether it is a business, a not-for-profit organization, or government body. Management includes the activities of setting the strategy of an organization and coordinating the efforts of its employees (or of volunteers) to accomplish its objectives through the application of available resources, such as financial, natural, technological, and human resources. The term "management" may also refer to those people who manage an organization.
Security
Security is freedom from, or resilience against, potential harm (or other unwanted coercive change) from external forces. Beneficiaries (technically referents) of security may be persons and social groups, objects and institutions, ecosystems, and any other entity or phenomenon vulnerable to unwanted change by its environment.
System
A system is a regularly interacting or interdependent group of items forming an integrated whole. Every system is delineated by its spatial and temporal boundaries, surrounded and influenced by its environment, described by its structure and purpose and expressed in its functioning.
Security
To bargain freedom for security is the devil's bargain. Having made the bargain, one enjoys neither freedom nor security.
Gerry Spence, Give Me Liberty! Freeing Ourselves in the Twenty-First Century, Ch. 16 : Security, the One-Way Ticket to Slavery, p. 174 (1998)
System
In the most abstract sense, a system is a set of objects together with relationships among the objects. Such a definition implies that a system has properties, functions, and dynamics distinct from its constituent objects and relationships.
Tom R. Burns (2006) "System Theories" in: George Ritzer ed. The Encyclopedia of Sociology, Blackwell Publishing.
System
Everyone knows what engineering is. All that's left is to define systems, and I'm not fool enough to do that.
Robert Machol (1971) in: Paul Lewis "Mathmaticians Are Useful." The California Tech. May 6, 1971. p. 1: Machol explains his definition of systems engineering.