A parameter list, sometimes called an argument list, is a sequence of parameter declarations found in the header of a function, procedure, program or subroutine. All the parameters used in such types of code must be listed in the header of that function or procedure or the function must include a directive to where the parameters are listed, as is the case when using global parameters. The parameter list is basically just a list of the parameters and their characteristics, the parameter declarations. In some programming languages the entire parameter list is enclosed in parenthesis and each parameter declaration is separated from the next by a semicolon. Further each parameter declaration is composed of the parameter identifier, followed by a colon and the type identifier, and in some cases this is followed by symbols that assign the parameter a default value. The different parameter declarations are ordered in the parameter list. That is that there is a constraint or limiting attribute attached to an association to signify that the objects at one end are specified in some explicit order.

Parameters that can be transferred from one function or procedure to another have a transfer or passing protocol specified by its parameter list. Also the number and types of parameters that a function accepts and the number and types of values it returns are described in the parameter list. For a generic function all methods for that function must have congruent parameter lists.