a parameter for a composite type
A discriminant is a parameter of a composite type. It can control, for example, the bounds of a component of the type if that type is an array type. A discriminant of a task type can be used to pass data to a task of the type upon creation. (16)
A discriminant is a distinguished component of an object or value of a record type. The subtypes of other components, or even their presence or absence, may depend on the value of the discriminant.