ETYM Pref. para- + -meter: cf. French paramčtre.
Mathematics, a quantity that is constant in the case considered, but varies in other cases; a variable by the functions of which other variables can be expressed; generally, a measurement to which other measurements can be compared, a dimension.
Variable factor or characteristic. For example, length is one parameter of a rectangle; its height is another. In computing, it is frequently useful to describe a program or object with a set of variable parameters rather than fixed values.
For example, if a programmer writes a routine for drawing a rectangle using general parameters for the length, height, line thickness, and so on, any rectangle can be drawn by this routine by giving different values to the parameters.
Similarly, in a word-processing application that stores parameters for font, page layout, type of justification, and so on, these can be changed by the user.
1. A constant in the equation of a curve that can be varied to yield a family of similar curves; SYN. parametric quantity.
2. A quantity (such as the mean or variance) that characterizes a statistical population and that can be estimated by calculations from sample data.
3. Any factor that defines a system and determines (or limits) its performance.

In programming, a value that is given to a variable, either at the beginning of an operation or before an expression is evaluated by a program. Until the operation is completed, a parameter is effectively treated as a constant value by the program. A parameter can be text, a number, or an argument name assigned to a value that is passed from one routine to another. Parameters are used as a means of customizing program operation. See also argument, pass by address, pass by value, routine.