What does dictionary mean?
A dictionary is a reference resource that lists the words of a language — or the terms of a particular field — usually in alphabetical order, providing each entry's spelling, pronunciation, part of speech, definition, and frequently its origin and examples of use. Dictionaries exist in print and digital form, ranging from pocket editions to vast online databases updated continuously. The word also extends naturally into other domains: bilingual dictionaries translate between languages, specialized dictionaries cover subjects such as medicine or law, and in computing a 'dictionary' is a data structure that maps keys to values. As a common noun, it is neutral in register and appears everywhere from classrooms to newsrooms. Figuratively, phrases like 'a walking dictionary' praise someone with extensive vocabulary knowledge. Few books shape how we understand language as directly: dictionaries record not just what words mean, but how those meanings shift over time, making them both practical tools and historical records.
nounA reference book or online resource that lists the words of a language (or a specialized subject), typically in alphabetical order, giving their meanings, pronunciations, and often their origins and usage.
- A reference work listing the words of a language alphabetically with their meanings, pronunciations, and other information.
- A similar reference work for a specialized field or domain, listing terms with definitions.
- (Computing) A data structure or file mapping keys to values.
"She kept a well-thumbed dictionary on her desk and consulted it daily while learning Spanish."
"The editor reached for a dictionary to verify the obscure word's etymology."
"In Python, a dictionary stores key–value pairs and allows fast lookups by key."
Standard plural: words ending in -ary form their plural in -aries.
"The library keeps several authoritative dictionaries on open shelves."
The word 'dictionary' didn't appear in English until the early 1500s — before that, people simply had no single name for a book of words.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of dictionary
The word dictionary comes from medieval Latin 'dictionarium', literally a 'collection of words and phrases', derived from Latin 'dictio' meaning 'a saying or word', which in turn comes from the verb 'dicere', 'to say'. It entered English in the early 16th century. It shares its root with related words built on the same Latin stem, including diction, dictate, predict, and contradict.
How dictionary is actually used
Neutral in register and used in all varieties of English. In computing contexts, 'dictionary' has a specific technical sense as a key–value data structure; in linguistics, 'lexicon' is often preferred. British dictionaries traditionally list '-ize' spellings under '-ise' variants and vice versa, so 'dictionary' itself carries no strong regional variant forms.
Easily confused with dictionary
A dictionary defines words and explains their meanings, while a thesaurus groups words by similarity of meaning to help find synonyms and antonyms.
Lexicon means essentially the same thing as dictionary but is more formal or technical, often referring to the vocabulary of a particular language, person, or field.