1. Mathematics
   1. A constant in an equation that varies in other equations of the same general form, especially such a constant in the equation of a curve or surface that can be varied to represent a family of curves or surfaces.
   2. One of a set of independent variables that express the coordinates of a point.
   3. One of a set of measurable factors, such as temperature and pressure, that define a system and determine its behavior and are varied in an experiment.
   4. Usage Problem A factor that restricts what is possible or what results: "all the parameters of shelter—where people will live, what mode of housing they will choose, and how they will pay for it" (New York).
   5. A factor that determines a range of variations; a boundary: an experimental school that keeps expanding the parameters of its curriculum.
2. 1. One of a set of measurable factors, such as temperature and pressure, that define a system and determine its behavior and are varied in an experiment.
   2. Usage Problem A factor that restricts what is possible or what results: "all the parameters of shelter—where people will live, what mode of housing they will choose, and how they will pay for it" (New York).
   3. A factor that determines a range of variations; a boundary: an experimental school that keeps expanding the parameters of its curriculum.
3. Statistics A quantity, such as a mean, that is calculated from data and describes a population.
4. Usage Problem A distinguishing characteristic or feature.

Usage Note: The term parameter, which originates in mathematics, has a number of specific meanings in fields such as astronomy, electricity, crystallography, and statistics. Perhaps because of its ring of technical authority, it has been used more generally in recent years to refer to any factor that determines a range of variations and especially to a factor that restricts what can result from a process or policy. In this use it often comes close to meaning "a limit or boundary." Some of these new uses have a clear connection to the technical senses of the word. For example, the provisions of a zoning ordinance that limit the height or density of new construction can be reasonably likened to mathematical parameters that establish the limits of other variables. Therefore one can say The zoning commission announced new planning parameters for the historic Lamping district of the city. But other uses go one step further and treat parameter as a high-toned synonym for characteristic. Eighty percent of Panelists reject this use of parameter in the example The Judeo-Christian ethic is one of the important parameters of Western culture. · Some of the difficulties with the nontechnical use of parameter appear to arise from its resemblance to the word perimeter, with which it shares the sense "limit," though the precise meanings of the two words differ. This confusion probably explains the use of parameter in a sentence such as U.S. forces report that the parameters of the mine area in the Gulf are fairly well established, where the word perimeter would have expressed the intended sense more exactly. This example of a use of parameter was unacceptable to 61 percent of the Usage Panel.