Can a candidate key for a composite attribute be called a composite key?

Question

Let's take an example of student entity type

• Name
• Class
• Section
• Address (Line1, Line2, City, State, Country, PinCode)

Since composite attribute holds multiple atomic attributes, such that the group is treated as single attribute. It is similar to how we perceive structures in C programming. If I add a constraint key on Address field, will it be called composite key?

Or the composite key must have two or more attributes for example (ignoring the semantics) the combinations like

• {Class, Section}
• {Class, Address}
• {Name, Class, Section}