What does it mean when a dictionary is not a sequence?

When someone mentions a 'dictionary' it typically conjures up an image of being able to search for a word, phrase or definition. To most people, a 'dictionary' means a tool for looking up words and their associated meaning. However, what does it mean when the term 'dictionary' is used in contexts that do not involve searching for definitions?

A dictionary is actually a data structure in which its elements are stored in a way that makes them easy to access. These elements can be numbers, characters or words, as well as other types of information. A dictionary is a type of collection where each element stores both keys and values; the keys represent the elements and the values represent more information about those elements.

The actual definition of a dictionary is that it is not necessarily always organized into an ordered sequence such as that found with lists, arrays or queues. Instead, the data structure provides fast lookup time with its key-value pairs that allow for efficient queries. In this context, dictionaries are typically implemented as hash tables –this means that when searching through a given set (like the English language), only the key of an element (the word) needs to be known in order to retrieve the value (the definition). This quick access makes using dictionaries convenient and more efficient than other data structures such as linked lists or trees which require iterations throughout the entire structure before most items can be found.

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