From WordNet (r) 3.0 (2006) :
parameter
n 1: a constant in the equation of a curve that can be varied to
yield a family of similar curves [syn: parameter,
parametric quantity]
2: any factor that defines a system and determines (or limits)
its performance
3: (computer science) a reference or value that is passed to a
function, procedure, subroutine, command, or program [syn:
argument, parameter]
4: a quantity (such as the mean or variance) that characterizes
a statistical population and that can be estimated by
calculations from sample data