The word argument is used in several differing contexts in mathematics. The most common usage refers to the argument of a function, but is also commonly used to refer to the complex argument or elliptic argument.
An argument of a function 
is one of the 
parameters on which the function's value depends. For example,
the sine 
is a one-argument function, the binomial
coefficient 
is a two-argument function, and the hypergeometric
function 
is a four-argument function.
