Underground economy: illegal business practices where commerce and the income derived from it are unreported. The practices are typically associated with bartering and the sale of goods and services for cash. Drug dealing, prostitution, and gambling are major segments of the underground economy.
Unified Command System (USC): a management structure to facilitate public and private cooperation to bring together expertise and resources for managing and resolving a critical incident. It involves joint consultation and decision-making.
Unity of command: a management concept that each individual in an organization should be accountable to only a single superior.
Unity of direction: a management concept that there should be only one head and one plan for each organizational segment.