Coenetic variables are those varying factors which are **common to a system and its environment and affect both**. Very often they are not recognized as such, because the boundaries of the system are drawn so as to exclude them. Through directive correlation, coenetic variables act to reduce the variety operating between a system and its environment and narrow the field in which adaptation occurs. The action of coenetic variables is one of the reasons that it is sometimes difficult to distinguish, or fix over time, the boundaries between systems and their environments. The same set of coenetic variables can have very different effects on different parts of the environment. A snowstorm, for example, will be greeted as a boon to winter resort operators and a disaster to a shopkeeper who stocks highly perishable or date-specific goods. # SOURCE Sommerhoff, G. (1950). Analytical Biology. London: Oxford University Press. Sommerhoff, G. (1974). Logic of the living brain. London: Wiley. The word coenetic (pronounced sennetic) was coined by Sommerhoff from the Greek word meaning 'common'. # EXAMPLES • the effect of change in interest rates on the build-up of inventory and the terms offered to retailers • **weather**--the amount of rainfall on the harvest date and yield • the change in traffic patterns resulting from the temporary closing of a major artery • the impact of economic conditions on business investment # NON-EXAMPLES • the behavior of a supervisor towards a subordinate• the interaction of players in a game of chance • the drop of support suffered by a political candidate charged with a crime • the reaction of chemicals in a test tube when other factors are held constant # PROBABLE ERROR • not allowing for the effect of coenetic variables on the reduction of variety in a system'sbehavior • misidentifying a coenetic variable as a link in a cause-effect chain # SEE Directive Correlation; Adaptation; System; Boundary; Environment