Agency costs: The economic term for the discrepancy between the performance of a task by the interested party (the principal in economic terms) compared with its performance by an appointee (an agent in economic terms).

Agent: A term that may cause much misunderstanding between lawyers and economists. As a legal term it means a representative with authority to transact in the name of the principal. As an economic term it most often means someone who administers another's interests even if without representing the principal. Occasionally, economists use the term agent as individual when describing a model, for example, “a society consists of N agents, who …”

At the money: A colloquial expression that is applied to a right, usually an option or a claim in bankruptcy. It means that the right is near its nominal value. In the case of an option it means that the market price of the underlying security is near the strike price. In the case of a claim in bankruptcy it means that the value of the estate is sufficient to repay other claims with greater seniority but not to repay more junior claims. Compare in the money, out of the money.

Average deviation: A measure of the dispersion of a distribution that consists of the average difference from the distribution's average.

Average: The center of a symmetric distribution or a measure of centrality of a distribution that is not symmetric. See also mean.

axis: See x axis, y axis, z axis.