ETYM French contrôle a counter register, contr. from contr-rôle; contre (Latin contra) + rôle roll, catalogue. Related to Counter and Roll, Counterroll.
1. Power to direct or determine.
2. A mechanism that controls the operation of a machine; SYN. controller.
3. A relation of constraint of one entity (thing or person or group) by another.
4. A spiritual agency that is assumed to assist the medium during a seance.
5. (Physiology) Regulation or maintenance of a function or action or reflex etc.
6. The activity of managing or exerting control over something; SYN. controlling.
7. The economic policy of controlling or limiting or curbing prices or wages etc.

1. To exercise authoritative control or power over; SYN. command.
2. To lessen the intensity of; temper; hold in restraint; hold or keep within limits; SYN. hold in, hold, contain, check, curb, moderate.
3. To verify by using a duplicate register for comparison.
4. To verify or regulate by conducting a parallel experiment or comparing with another standard, of scientific experiments; SYN. verify.

In biology, the process by which a tissue, an organism, a population, or an ecosystem maintains itself in a balanced, stable state. Blood sugar must be kept at a stable level if the brain is to function properly, and this steady-state is maintained by an interaction between the liver, the hormone insulin, and a detector system in the pancreas.
In the ecosystem, the activities of the human race are endangering the balancing mechanisms associated with the atmosphere in general and the greenhouse effect in particular.

1. Management of a computer and its processing abilities so as to maintain order as tasks and activities are carried out. Control applies to measures designed to ensure error-free actions carried out at the right time and in the right order relative to other data-handling or hardware-based activities. In reference to hardware, control of system operations can reside in a data pathway called a control bus. In reference to software, control refers to program instructions that manage data-handling tasks.
2. In a graphical user interface, an object on the screen that can be manipulated by the user to perform an action. The most common controls are buttons, which allow the user to select options, and scroll bars, which allow the user to move through a document or position text in a window.