functionargument

Function argument refers to a value supplied to a function when it is called. Arguments are matched to the parameters declared in the function's signature. A parameter is a variable name in the function definition, and an argument is the actual value provided at call time. For example, in def f(x, y): return x + y, the parameters are x and y; calling f(2, 3) passes the arguments 2 and 3.

Languages differ in how arguments are supplied and interpreted. Common forms include positional arguments, where values are assigned by position; and keyword or named arguments, where values are associated with parameters by name. Many languages also support default, optional, or variadic arguments. In Python, a function can declare def f(a=1, b=2): and callers may pass positional or keyword arguments; Python also supports *args for variable-length positional arguments and **kwargs for variable-length keyword arguments.

In terms of evaluation and passing semantics, arguments may be passed by value or by reference in different languages. For example, C and C++ support both, with varying effects on the caller's variables. In Java, arguments are passed by value; for object types, the value is a copy of the reference, so the callee can modify the object but cannot rebind the caller's reference. Other languages provide rest parameters (JavaScript) or variadic functions (C, Java) using specialized syntax.

Proper handling of function arguments—validation of types, ranges, and invariants—constitutes a standard part of function design and helps ensure reliable and predictable behavior.