Final answer:
A composite key is one where multiple keys are needed to identify a tuple uniquely in a database management system.
Step-by-step explanation:
In database management systems, a composite key is one where multiple keys are needed to identify a tuple uniquely. It consists of two or more attributes that together uniquely identify each tuple in a table. These attributes could be simple primary keys or a combination of multiple keys.
For example, consider a student database where a student's ID, name, and date of birth together form a composite key. The combination of these attributes ensures the uniqueness of each student in the database.