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The longest word in a major dictionary
The word most often cited as the longest in a major English dictionary is pneumonoultramicroscopicsilicovolcanoconiosis, a 45-letter medical term for a lung disease caused by breathing in very fine ash or silica dust. It appears in the Oxford English Dictionary. Like many extremely long words, it was built by joining existing word parts (pneumono-, ultra-, microscopic-, silico-, volcano-, -coniosis) rather than coined as a single new word from scratch, which is how it reached 45 letters.
Other well-known long words
A few shorter, more commonly used long words also come up often in this discussion.
- Antidisestablishmentarianism (28 letters): opposition to withdrawing state support from an established church.
- Floccinaucinihilipilification (29 letters): the act of judging something to be worthless.
- Supercalifragilisticexpialidocious (34 letters): a nonsense word popularized by the film Mary Poppins, not a standard dictionary headword.
Why "the longest word" is hard to pin down
Claims about the single longest word in English depend heavily on what counts as a real word. Chemical names can be extended almost indefinitely by adding more components: the systematic chemical name for the protein titin runs to well over 100,000 letters, but dictionaries exclude it because it is a generated chemical formula rather than a word anyone actually uses in a sentence. Similarly, a writer can always coin a longer word by joining more prefixes and suffixes together, which is why dictionaries generally only count words that have some record of real use.
Frequently asked questions
What is the longest word in the English dictionary?
Pneumonoultramicroscopicsilicovolcanoconiosis, a 45-letter medical term for a lung disease, is the word most often cited as the longest entry in a major English dictionary.
Is supercalifragilisticexpialidocious a real word?
It is a nonsense word invented for the film Mary Poppins rather than a standard dictionary headword, even though it is widely recognized.
Why do chemical names get excluded from "longest word" lists?
Chemical names such as the one for the protein titin are generated systematically and can run past 100,000 letters, so dictionaries treat them as formulas rather than words in ordinary use.
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