parameter

(noun) a constant in the equation of a curve that can be varied to yield a family of similar curves. Synonyms: parametric quantity.

(noun) any factor that defines a system and determines (or limits) its performance.

(noun) (computer science) a reference or value that is passed to a function, procedure, subroutine, command, or program. Synonyms: argument.

(noun) a quantity (such as the mean or variance) that characterizes a statistical population and that can be estimated by calculations from sample data.