Final answer:
An attribute is dependent on a second attribute if a value for the first attribute determines a single value for the second attribute at any time.
Step-by-step explanation:
An attribute is dependent on a second attribute if a value for the first attribute determines a single value for the second attribute at any time. This concept is commonly known as functional dependency in database management systems.
For example, in a table of students, if the student ID is the first attribute and the student's name is the second attribute, then the name attribute is dependent on the student ID attribute because given a specific student ID, there is only one corresponding name value.
Functional dependencies play a crucial role in database design and normalization.