Which of the following describes an attribute in a relational database?

An attribute in a relational database refers to a property or characteristic of an entity that is represented within that database. For instance, if an entity is a "Customer," attributes might include "Customer ID," "Name," "Email Address," and "Phone Number." These attributes help to define the details about the entity and are typically represented as columns in a table within the database.

This understanding is key to effective database design and querying, as attributes determine the data that can be stored and accessed for each entity.

The other choices do not accurately describe attributes in a relational database: a row refers to a single record in a table, attributes can include non-numeric data types such as text or dates, and a key is a specific attribute or a set of attributes used to uniquely identify a record, not a synonym for all attributes.