What defines the maximum number of times an instance in one entity can be associated with instances in a related entity?

Cardinality is the concept that defines the maximum number of instances in one entity that can be associated with instances in a related entity within a database or an entity-relationship model. It provides critical information about relationships between entities, specifying how many instances of one entity can relate to instances of another. For instance, in a one-to-many relationship, one instance of the first entity can be associated with multiple instances of the second entity, while the second entity can be associated with only one instance of the first entity.

In contrast, the other options describe different concepts within software development and database design. Modularity relates to designing systems in a way that separates functionality into interchangeable modules. Inheritance is a principle from object-oriented programming that allows one class to inherit properties and behaviors from another class. Aggregation refers to a relationship where a whole is made up of parts, but it doesn't define cardinality. Understanding these distinctions clarifies why cardinality is the relevant answer to the question posed.