Longest word in English

There are endless debates over what is the longest word in the English language, and these debates revolve around the terms of consideration. If scientific or technical terms are allowed wholesale, then there is a potential for words of indescribable length, particularly in regard to the naming of organic and biological compounds such as proteins, such as Methionylglutaminy...serine (q.v.).

Popular usage

Antidisestablishmentarianism (a movement opposed to the separation of church and state) at 28 letters is often popularly accepted as English's longest word, and is probably the best-known "longest word."

A coined term

The word pneumonoultramicroscopicsilicovolcanoconiosis (defined as "a lung disease caused by the inhalation of very fine silica dust"), at 44 letters is certainly the longest word ever to appear in a non-technical dictionary of English (Source: OED). However there are strong indications that the word was coined by puzzler Everett Smith in 1935 as a hypothetical long word that could result from the protraction of medical terms. The actual name of the disease is pneumoconiosis.

Other long words

Everett Smith's prediction seems to have been proven true by the 207,000+ letter word cited by the Guinness Book of Records which allegedly represents the name for human mitochondrial DNA.

The longest word which appears in William Shakespeare's works is the 27 letter honorificabilitudinitatibus. This is arguably an English word, but only because he used it.

The well-known song-title from the movie Mary Poppins Supercalifragilisticexpialidocious with 34 letters does appear in several dictionaries, but only as a proper noun, and defined in reference to the song title. Hence it may well be dismissed as a "real" word.

The Guinness Book of Records in 1992 (and subsequent editions) declares the "longest real word" in the English language to be floccinaucinihilipilification at 29 letters. Defined as the act of estimating as worthless, its usage has been recorded as far back as 1741. In recent times its usage has been recorded in the proceedings of the US Senate (Senator Jesse Helms used the word in 1999 during the debate on the Comprehensive Test Ban Treaty [Randolph V. Cinco]) and at the White House (by Press Secretary Mike McCurry in his December 6, 1995, White House Press Briefing).

The character Big Bird of Sesame Street sings the Latin alphabet, thinking it is a word. He reads Abcdefghijklmnopqrstuvwxyz aloud as "(ab-cud-ef-gï)(jek'l-m'nâp-kwûr)(stööv-wik-ziz)" and breaks into song.

Constructions

It should be noted that English is a language which permits the legitimate extension of existing words to serve new purposes by the addition of prefixes and suffixes. This is sometimes referred to as agglutinative construction. As an example, one of the longest words used in the Wikipedia is contraneoantidisestablishmentarianalistically at 45 letters (although there are reasons to believe this was somewhat contrived). The length of this word is enhanced by the use of "contra" and especially the suffix "-alistically" which can frequently be added to words ending in "-tion" (eg. nationalistically, traditionalistically, floccinaucinihilipilificationalistically).

The word nonetheless is an interesting study in just how complex a word can legitimately be assembled. This word can be analysed as follows:

establish - to set up, put in place, or institute (originally from the Latin stāre, to stand)
establish-ment - something established, in particular a church instituted by law, such as the Church of England.
dis-establishment - the separation of church and state (specifically in this context it is the political movement of the 1860s in Britain)
disestablishment-arian - a person in support of the movement designed to bring about the above (hereafter called the 'first' movement).
anti-disestablishmentarian - a person belonging to the movement opposed to the first movement.
neo-antidisestablishmentarian - a person belonging to the new version of the movement opposed to the first movement. (Appropriate because in this context the original antidisestablishment movement had become defunct).
contra-neoantidisestablishmentarian - a person belonging to the movement opposed to the new version of the movement opposed to the first movement.
contraneoantidisestablishmentarian-alistically - behaving in the manner of a person belonging to the movement opposed to the new version of the movement opposed to the first movement.

It could be further extended as follows:

pseudo-contraneoantidisestablishmentarianalistically - false behaviour in the manner of a person belonging to the movement opposed to the new version of the movement opposed to the first movement.
pro-pseudocontraneoantidisestablishmentarianalistically - in favour of the false behaviour in the manner of a person belonging to the movement opposed to the new version of the movement opposed to the first movement.

Also see A long word from Ancient Greek

Technical terms

A number of scientific naming schemes can be used to generate arbitrarily long words.

The systematic convention for naming chemical elements of large atomic number is open-ended, for example unbitriquadpenthexseptoctennillium is the name of a hypothetical element with atomic number 1234567890.

John Horton Conway and Landon Curt Noll developed an open-ended system for naming powers of 10, in which one sexmilliaquingentsexagintillion is the name for 10¹⁹⁶⁸³.

The IUPAC nomenclature for organic chemical compounds is open-ended. In this system, the molecule constituting "Tobacco Mosaic Virus, Dahlemense Strain" is named:

Acetylseryltyrosylserylisoleucylthreonylserylprolylserylglutaminylphenylalanylvalylphenylalanylleucylserylserylvalyltryptophylalanylaspartylprolylisoleucylglutamylleucylleucylasparaginylvalylcysteinylthreonylserylserylleucylglycylasparaginylglutaminylphenylalanylglutaminylthreonylglutaminylglutaminylalanylarginylthreonylthreonylglutaminylvalylglutaminylglutaminylphenylalanylserylglutaminylvalyltryptophyllysylprolylphenylalanylprolylglutaminylserylthreonylvalylarginylphenylalanylprolylglycylaspartylvalyltyrosyllysylvalyltyrosylarginyltyrosylasparaginylalanylvalylleucylaspartylprolylleucylisoleucylthreonylalanylleucylleucylglycylthreonylphenylalanylaspartylthreonylarginylasparaginylarginylisoleucylisoleucylglutamylvalylglutamylasparaginylglutaminylglutaminylserylprolylthreonylthreonylalanylglutamylthreonylleucylaspartylalanylthreonylarginylarginylvalylaspartylaspartylalanylthreonylvalylalanylisoleucylarginylserylalanylasparaginylisoleucylasparaginylleucylvalylasparaginylglutamylleucylvalylarginylglycylthreonylglycylleucyltyrosylasparaginylglutaminylasparaginylthreonylphenylalanylglutamylserylmethionylserylglycylleucylvalyltryptophylthreonylserylalanylprolylalanylserine

Another word in the IUPAC system, a scientific name for tryptophan synthetase, which is made up of 267 amino acids, has appeared written down a number of times and has 1,909 letters. According to the Guinness Book of Records, 18th edition, it is the longest chemical word for C₁₂₈₉H₂₀₅₁N₃₄₃O₃₇₅S₈:

methionylglutaminylarginyltyrosylglutamylserylleucylphenylalanylalanylglutaminylleucyllysylglutamylarginyllysylglutamylglycylalanylphenylalanylvalylprolylphenylalanylvalylthreonylleucylglycylaspartylprolylglycylisoleucylglutamylglutaminylserylleucyllysylisoleucylaspartylthreonylleucylisoleucylglutamylalanylglycylalanylaspartylalanylleucylglutamylleucylglycylisoleucylprolylphenylalanylserylaspartylprolylleucylalanylaspartylglycylprolylthreonylisoleucylglutaminylasparaginylalanylthreonylleucylarginylalanylphenylalanylalanylalanylglycylvalylthreonylprolylalanylglutaminylcysteinylphenylalanylglutamylmethionylleucylalanylleucylisoleucylarginylglutaminyllysylhistidylprolylfrellthreonylisoleucylprolylisoleucylglycylleucylleucylmethionyltyrosylalanylasparaginylleucylvalylphenylalanylasparaginyllysylglycylisoleucylaspartylglutamylphenylalanyltyrosylalanylglutaminylcysteinylglutamyllysylvalylglycylvalylaspartylserylvalylleucylvalylalanylaspartylvalylprolylvalylglutaminylglutamylserylalanylprolylphenylalanylarginylglutaminylalanylalanylleucylarginylhistidylasparaginylvalylalanylprolylisoleucylphenylalanylisoleucylcysteinylprolylprolylaspartylalanylaspartylaspartylaspartylleucylleucylarginylglutaminylisoleucylalanylseryltyrosylglycylarginylglycyltyrosylthreonyltyrosylleucylleucylserylarginylalanylglycylvalylthreonylglycylalanylglutamylasparaginylarginylalanylalanylleucylprolylleucylasparaginylhistidylleucylvalylalanyllysylleucyllysylglutamyltyrosylasparaginylalanylalanylprolylprolylleucylglutaminylglycylphenylalanylglycylisoleucylserylalanylprolylaspartylglutaminylvalyllysylalanylalanylisoleucylaspartylalanylglycylalanylalanylglycylalanylisoleucylserylglycylserylalanylisoleucylvalyllysylisoleucylisoleucylglutamylglutaminylhistidylasparaginylisoleucylglutamylprolylglutamyllysylmethionylleucylalanylalanylleucyllysylvalylphenylalanylvalylglutaminylprolylmethionyllysylalanylalanylthreonylarginylserine

Place names

There is some debate as to whether or not a place name is a legitimate word. Without entering that debate, let it be noted that the longest officially recognized place name in an English-speaking country is Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuakitanatahu (85 letters) which is a hill in New Zealand.

The 58 letter name Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch is the famous name of a town in Wales in the United Kingdom. Critics, however, have alleged that the name (which was adopted in the mid 19th century) was contrived solely to be "the longest name of a town in Britain". The longest station name in the UK, at 68 letters, is Gorsafawddacha'idraigodanheddogleddollônpenrhynareurdraethceredigion which was contrived to beat the Welsh Town.

The longest place name in the United States (45 letters) is Chargoggagoggmanchauggagoggchaubunagungamaugg. The longest hyphenated name in the U.S. is Winchester-on-the-Severn, a town in Maryland.

It is questionable whether any of the above are properly considered English words, being derived from Maori, Welsh, and Native American words respectively.

Sesquipedalianism

Although only seventeen letters long, sesquipedalianism deserves a mention. It was used as a nonce word by the Roman author Horace, in his work "Ars Poetica" (The Art of Poetry). The quote is as follows: "Proicit ampullas et sesquipedalia verba," which means, "He throws aside his paint pots and his words that are a foot and a half long". The word sesquipedalianism means "the practice of using words one and half feet long".

Jokes

A popular joke answer to this question is the word smiles, credited as the longest word because there is a mile between each s.