What characteristic does a dictionary data structure have?

A dictionary data structure is characterized by its use of unordered pairs of keys and values. This means each entry consists of a unique key that maps to a corresponding value, allowing for efficient data retrieval. The keys in a dictionary are used to look up the values, making it a very effective structure for situations where quick access to data is required.

The unordered aspect is significant; unlike arrays, which maintain a specific sequence, dictionaries do not rely on the order in which elements are added. This allows for flexibility and quick access based on the keys rather than their position.

Other options misrepresent the nature of dictionaries. For instance, being identical to an array is incorrect because arrays are ordered collections that can store elements in a defined sequence. Requiring all keys to be similar types is also inaccurate; dictionaries can have keys of varying data types. Lastly, the assertion that dictionaries only store numerical data ignores the fact that they can hold a wide variety of data types, including strings, lists, and even other dictionaries as values.