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pa·ram·e·ter (pə-rămĭ-tər)
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n.
1. Mathematics
a. 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.
b. One of a set of independent variables that express the coordinates of a point.
2.
a. 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.
b. Usage Problem A factor that restricts what is possible or what results: "all the parameters of shelterwhere people will live, what mode of housing they will choose, and how they will pay for it" (New York).
c. 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.

[New Latin parametrum, a line through the focus and parallel to the directrix of a conic : Greek para-, beside; see PARA-1 + Greek metron, measure; see -METER.]

para·metric (părə-mĕtrĭk), para·metri·cal adj.
para·metri·cal·ly adv.

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, people have applied parameter more generally in recent years to refer to any factor that determines a range of variations and especially to a factor that restricts what results from a process or policy. In this use, the word parameter is used to mean "the particular value of a parameter," and comes close to meaning "a set limit or boundary." For example, a budget can be thought of as a set of parameters that determine a range of activity, much like a set of mathematical parameters that establish the range of effects, or limits, of other variables. The sentence A budget is a framework that defines the financial parameters within which an organization operates was considered acceptable by 81 percent of the Usage Panel in our 2004 survey. Parameter is sometimes used incorrectly when it does not denote a range of variation, as if it were a technical-sounding synonym for characteristic. In 1988, 88 percent of the Usage Panel rejected the sentence The Judeo-Christian ethic is one of the important parameters of Western culture. In 2004, 77 percent rejected this same sentence, suggesting that familiarity has not bred tolerance of this usage.

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2017 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
 

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