1. A reference book: This is the most common meaning. A dictionary is a book that lists words in alphabetical order and provides their meanings, pronunciations, and often etymologies (origins of the word).
2. A collection of data: This meaning is used in the context of computer science. A dictionary in this sense is a data structure that allows you to store and retrieve data using key-value pairs. For example, a dictionary could store the names of people and their phone numbers.
3. A vocabulary: In a more informal sense, "dictionary" can also refer to a person's vocabulary or the vocabulary of a specific subject.
Here are some examples:
* "I looked up the meaning of the word 'serendipity' in the dictionary." (reference book)
* "The software uses a dictionary to store the user's preferences." (data structure)
* "The dictionary of medical terms is very comprehensive." (vocabulary)
Let me know if you'd like me to elaborate on any of these meanings!