parameter

Etymology

From French paramètre, from New Latin parametrum (“parameter”), from Ancient Greek παρα- (para-, “beside”) + μέτρον (métron, “measure”).

noun

1. A value kept constant during an experiment, equation, calculation, or similar, but varied over other versions of the experiment, equation, calculation, etc.
   As molecular surface-to-surface contacts control both solution phenomena and surface phenomena, it is not surprising that various correlations of cohesion parameters and surface phenomena can be found. 2007, Charles M. Hansen, Hansen Solubility Parameters
   The independent parameters of a system or network over F(z) reflect its structure and determine its structural properties (such as the reducibility of coefficient matrix A and its characteristic polynomial det(λI −A), controllability and observability over F(z), etc.). 2012, Kai-Sheng Lu, Rational Function Systems and Electrical Networks with Multi-Parameters
   On the other hand, if we have suitable data, we may be able to develop some direct computational methods for the essentially nonlinear parameter identification problems, in which fewer or even no nonlinear processes are involved. 2014, M. Amouroux, A. El Jai, Control of Distributed Parameter Systems 1989
2. (sciences) A variable that describes some system (material, object, event, etc.) or some aspect thereof.
   1. (statistics) Any measured quantity of a statistical population that summarises or describes an aspect of the population.
   2. (machine learning) A variable of a model that is trained by a machine learning algorithm.
      Coordinate term: feature
      The parameter estimation problem considered in this chapter consists of estimating the unknown parameter, ū [a barred v, actually], given N samples of the observation process. 2012, Michael Lemmon, Competitively Inhibited Neural Networks for Adaptive Parameter Estimation, Springer Science & Business Media, page 74
      Fundamental is the regulation of a for-profit OpenAI. The company initially delayed the launch of its earlier GPT-2, with a mere 1.5bn parameters, because the company fretted over its implications. 2020-08-11, “The Guardian view on artificial intelligence's revolution: learning but not as we know it”, in The Guardian
3. (programming) An input variable of a function definition, that gets an actual value (argument) at execution time.
4. (programming, loosely) An actual value given to such a formal parameter.
5. A characteristic or feature that distinguishes something from others.
6. (geometry) In the ellipse and hyperbola, a third proportional to any diameter and its conjugate, or in the parabola, to any abscissa and the corresponding ordinate.
   The parameter of the principal axis of a conic section is called the latus rectum.
7. (crystallography) The ratio of the three crystallographic axes which determines the position of any plane.
8. (crystallography) The fundamental axial ratio for a given species.