What do you call a collection of key-value pairs where each key is unique?

A collection of key-value pairs where each key is unique is referred to as a map or dictionary. These data structures are designed to store data in pairs, with the key serving as a unique identifier that maps to a specific value. This uniqueness of keys allows for efficient data retrieval, as you can quickly access a value associated with a specific key without needing to sift through all the elements.

In a dictionary or map, operations such as adding, retrieving, or deleting entries are efficient, often operating in constant time (O(1)) on average, due to the underlying implementation typically using hash tables. This makes maps and dictionaries particularly useful for situations where associative relationships between keys and values need to be established and managed, such as in lookup tables, caches, or configuration settings.

In contrast, the other options present different types of data structures. An array is a collection of items stored at contiguous memory locations, and while it can store multiple values, it does not inherently enforce unique keys. A set is a collection of distinct items but does not store them as key-value pairs. Lastly, a list is an ordered collection of elements where duplicates are allowed, but it also does not utilize keys for accessing values. Thus, the unique key-value pairing characteristic is