Aggregation in the context of a gradebook refers to the method or formula used to calculate a student's overall grade based on the scores of the weighted grade items and categories. It determines how the scores are combined to produce the final grades.

Explanation: There are various aggregation methods, such as weighted means of grades, simple weighted means of grades, means of grades (with extra credit), natural, that can be used to calculate a student's final grades. The choice of aggregation depends on how you want to calculate and represent the overall performance.