What is the longest word in the dictionary?

Answer 1

The longest words in the English dictionary are always debated. Some say some words are real words, some say they are not actual words. Some would exclude technical words, others exclude words which are no longer in use. 'Invented' words are also often excluded. Some dictionaries contend that other dictionaries include words that should not count as words.

The longest dictionary word* is pneumonoultramicroscopicsilico-volcanoconiosis

(45 letters, a coined word for a lung disease, sometimes with alternative ending -koniosis).

The longest unchallenged, non-technical word is antidisestablishmentarianism (28 letters).

Other long words include:

supercalifragilisticexpialidocious (34 letters). Coined for the film Mary Poppins. The meaning is uncertain.

floccinaucinihilipilification (29 letters) 'the action or habit of estimating as worthless.' Apparently invented by some university students to mean 'a lot of talk about nothing.'

honorificabilitudinitatibus (27 letters) Latin, meaning 'with honor' or 'able to achieve honors.' Used by Thomas Nashe in 1599 and by Shakespeare in Love's Labours Lost. Listed in Oxford English Dictionary.

hippopotomonstrosesquipedaliophobia (35 letters) A word coined/contrived, to mean 'fear of long words.' From 'hippopotomonstrosesquipedalian' (30 letters) listed in Mrs. Byrne's Dictionary of Unusual, Obscure and Preposterous Words. 1979.

* According to the Oxford English Dictionary, "pneumonoultramicroscopicsilico-volcanoconiosis is a factitious word alleged to mean 'a lung disease caused by the inhalation of very fine silica dust, causing inflammation in the lungs." A condition meeting the word's definition is normally called silicosis."

On the Lighter Side

The words "smiles" or "smiley" because there is a milebetween the first and last letters.

(For more information, see Sources and Related links below.)

Answer 2

Pneumonoultramicroscopic silicovolcanoconiosis, also called Black Lung.

Note: The break in the word doesn't really belong there, I put it there because the system would not accept the whole word unbroken.