The longest word in English depends upon the definition of what constitutes an English word. English allows new words to be formed by construction; long words are coined; place names may be considered words; technical terms may be arbitrarily long. Length can be in terms of orthography and number of written letters or phonology and the number of phonemes.
The longest word in any of the major English language dictionaries is pneumonoultramicroscopicsilicovolcanoconiosis, a 45-letter word which refers to a lung disease contracted from the inhalation of very fine silicious particles. Research has discovered that this word was originally intended as a hoax. It has since been used in a close approximation of its originally intended meaning, lending at least some degree of validity to its claim.
The longest non-technical word in major dictionaries is floccinaucinihilipilification at 29 letters. Consisting of a series of Latin words meaning "nothing" and defined as "the act of estimating something 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 United States Senate by Senator Robert Byrd , and at the White House by Bill Clinton's press secretary Mike McCurry, albeit sarcastically.
Antidisestablishmentarianism (a nineteenth century movement in England opposed to the separation of church and state) at 28 letters is still in colloquial currency for being one of the longest words in the English language.
The longest word which appears in William Shakespeare's works is the 27-letter honorificabilitudinitatibus, appearing in Love's Labour's Lost. This is arguably an English word (rather than Latin), only because it was Shakespeare who used it.
The humuhumunukunukuapua‘a, or reef triggerfish, is Hawaii's official state fish. At 22 letters (including the okina), it is one of the best known very long one-word names for an animal. It is occasionally quipped that the name is longer than the fish.
In his play Ecclesiazousae ("The Assemblywomen"), the ancient Greek comedic playwright Aristophanes created: Lopadotemachoselachogaleokranioleipsanodrimhypotrimmatosilphioparaomelitokatakechymenokichlepikossyphophattoperisteralektryonoptekephalliokigklopeleiolagoiosiraiobaphetraganopterygon, a word of 183 letters which describes a dish by stringing together its ingredients.
James Joyce made up nine 100 and one 101-letter words in his novel Finnegans Wake, the most famous of which is Bababadalgharaghtakamminarronnkonnbronntonnerronntuonnthunntrovarrhounawnskawntoohoohoordenenthurnuk. Appearing on the first page, it allegedly represents the symbolic thunderclap associated with the fall of Adam and Eve. As it appears nowhere else except in reference to this passage, it is generally not accepted as a real word. Sylvia Plath made mention of it in her semi-autobiographical novel The Bell Jar, when the protagonist was reading Finnegans Wake.
"Supercalifragilisticexpialidocious", the 34-letter title of a song from the movie Mary Poppins, does appear in several dictionaries, but only as a proper noun defined in reference to the song title. The attributed meaning is "a word that you say when you don't know what to say." The idea and invention of the word is credited to songwriters Robert and Richard Sherman.
In 1973, Pepsi's advertising agency Boase Massimi Pollitt used the a 100-letter but several-word term "Lipsmackinthirstquenchinacetastinmotivatingoodbuzzincooltalkinhighwalkinfastlivinevergivincoolfizzin" in TV and film advertising.
In 1975, the 71-letter (but several-word) advertising jingle Twoallbeefpattiesspecialsaucelettucecheesepicklesonionsonasesameseedbun was first used in a McDonald's Restaurant advertisement to describe the Big Mac sandwich.
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. This process can create arbitrarily long words: for example, the prefixes pseudo (false, spurious) and anti (against, opposed to) can be added as many times as desired. A word like anti-aircraft (pertaining to the defense against aircraft) is easily extended to anti-anti-aircraft (pertaining to counteracting the defense against aircraft, a legitimate concept) and can from there be prefixed with an endless stream of "anti-"s, each time creating a new level of counteraction. More familiarly, the addition of numerous "great"s to a relative, e.g. great-great-great-grandfather, can produce words of arbitrary length.
to set up, put in place, or institute (originally from the Latin stare, to stand)
ending the established status of a body, in particular a church, given such status by law, such as the Church of England
the separation of church and state (specifically in this context it is the political movement of the 1860s in Britain)
opposition to disestablishment
an advocate of opposition to disestablishment
the movement or ideology which opposes disestablishment
Of course, the process need not stop there: prefixes like neo- and contra- can be added, or -istically can be used in place of -ism.
A number of scientific naming schemes can be used to generate arbitrarily long words.
Gammaracanthuskytodermogammarus loricatobaicalensis is sometimes cited as the longest binomial name-it is a kind of amphipod. However, this name, proposed by B. Dybowski, was invalidated by the International Code of Zoological Nomenclature.
Aequeo: equal (Latin, aequo)
Salino: containing salt (Latin, salinus)
Calcalino: calcium (Latin, calx)
Ceraceo: "waxy" (Latin, cera)
Aluminoso: alumina (Latin)
Cupreo: from Copper
John Horton Conway and Landon Curt Noll developed an open-ended system for naming powers of 10, in which one sexmilliaquingentsexagintillion, coming from the Latin name for 6560, is the name for 103(6560+1) = 1019683. In British usage, it would be 106(6560) = 1039360.
The longest published word is the mathematical pattern abacaba...z...abacaba, a fractal word containing 67,108,863 characters. The pattern is constructed as follows: A, aBa, abaCaba, abacabaDabacaba, etc. The word occupies four 400-page volumes and is also the name of a character in a children's story.
Names of chemical compounds can be extremely long if written as one word, as is sometimes done. An example of this is sodiummetadiaminoparadioxyarsenobenzoemethylenesulphoxylate, an arsenic-containing drug. There are also other chemical naming systems, using numbers instead of "meta", "para" etc. as descriptive dividers, breaking up the name, which then no longer can be considered a single long word. One example, with 1,185 letters, is a chemical term referring to a Tobacco Virus.
The IUPAC nomenclature for organic chemical compounds is open-ended, giving rise to the 189,819-letter chemical name Methionylthreonylthreonyl...isoleucine, the shortened version of a protein also known as titin, or sometimes connectin, which is involved in striated muscle formation. Its chemical formula is C132983H211861N36149O40883S693.
There is some debate as to whether a place name is a legitimate word.
The longest officially recognized place name in an English-speaking country is Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuakitanatahu (85 letters) which is a hill in New Zealand.
The longest place name in the United States (45 letters) is Chargoggagoggmanchauggagoggchaubunagungamaugg, a lake in Webster, Massachusetts. It means "Englishmen at Manchaug at the Fishing Place at the Boundary" and is sometimes facetiously translated as "you fish your side of the water, I fish my side of the water, nobody fishes the middle". The lake is known to Americans as Webster Lake. The longest hyphenated names in the U.S. are Winchester-on-the-Severn, a town in Maryland, and Washington-on-the-Brazos, a notable place in Texas history.
The station sign at Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch in North Wales
The 58-character name Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch is the famous name of a town on Anglesey, an island of Wales. This place's name is actually 51 letters long, as certain character groups in Welsh are considered as one letter, for instance ll, ng and ch. It is generally agreed, however, that this invented name, adopted in the mid-19th century, was contrived solely to be the longest name of any town in Britain. The official name of the place is Llanfairpwllgwyngyll, commonly abbreviated to Llanfairpwll or the somewhat jocular Llanfair PG.
In Ireland, the longest English placename at 22 letters is Muckanaghederdauhaulia (from the Irish language, Muiceanach Idir Dhá Sháile, meaning "pig-marsh between two saltwater inlets") in County Galway. If this is disallowed for being derived from Irish, or not a town, the longest at 19 letters is Newtownmountkennedy in County Wicklow.
It is questionable whether any of the above (with the exception of Newtownmountkennedy) are properly considered English words, being derived from Maori, Nipmuck, Welsh and Irish words respectively, or being a conjunction of individual English words.
The longest multi-word place name in the world spelled in English is Krung Thep Mahanakhon Amon Rattanakosin Mahinthara Ayuthaya Mahadilok Phop Noppharat Ratchathani Burirom Udomratchaniwet Mahasathan Amon Piman Awatan Sathit Sakkathattiya Witsanukam Prasit, the formal ceremonial name for Bangkok, Thailand, meaning "The city of angels, the great city, the eternal jewel city, the impregnable city of God Indra, the grand capital of the world endowed with nine precious gems, the happy city, abounding in an enormous Royal Palace which resembles the heavenly abode where reigns the reincarnated god, a city given by Indra and built by Vishnukam".
A long place name in the US is "El Pueblo de Nuestra Señora la Reina de los Ángeles del Río de Porciúncula", ("The Town of Our Lady the Queen of the Angels of Porziuncola"). This place is now known as Los Angeles — a name which is still too long for some and is abbreviated as L.A.
Coincidentally, both are "the City of the Angels".
The longest hypothetically legal Scrabble word in North American play is ethylenediaminetetraacetates (28 letters). It is the plural of a word found in Merriam-Webster's Collegiate Dictionary, 10th edition, which was the dictionary of reference in North American Scrabble play for words of at least 10 letters until June 16, 2003. Naturally, this word is 'legal' in name only, since it would not fit on the board. There are many 15-letter words; the highest-scoring word on a Scrabble board is either benzoxycamphors (45) or sesquioxidizing (42). Because sesquioxidizing has the high-scoring Q and Z, it would score 62 × 27 = 1674 if played across an edge of the board with three triple word squares and two double letter squares involved. This is possible by the first player laying 'ox', the second player adding 'idizing' and the first player adding 'sesqui' to the beginning. Benzoxycamphors would score only 59 × 27 = 1593. Sesquioxidizing is not found in Webster's dictionary, although the roots of the word, sesquioxide and oxidizing, are.
Words with certain characteristics of notable length
The longest word in the English language containing only one vowel is strengths, while scraunched is the longest monosyllabic word in current usage. Twyndyllyngs is the longest word without any of the common vowel letters a, e, i, o, or u (although w and y function as vowels in this word). Euouae, a medieval musical term, is the longest English word consisting only of vowels, and the word with the most consecutive vowels. However, u was often used interchangeably with v, and the variant "evovae" is occasionally used.
The longest word whose letters are in alphabetical order is the eight-letter Aegilops, a grass genus. The seven-letter addeems (from the archaic verb addeem, meaning to award), alloquy (an archaic or literary word for an address), beefily (in a beefy manner), billowy (like a wave or surge), dikkops (a South African bird) and gimmors (plural of gimmor, an old-fashioned word for a mechanical contrivance) are also close.
The longest word typable with only the left hand (using conventional hand placement on a QWERTY keyboard) is tesseradecades, aftercataracts, or the more common but sometimes hyphenated sweaterdresses. Conversely, using the right hand alone, the longest word that can be typed is johnny-jump-up, or, excluding hyphens, hypolimnion. The longest word typable using only the top row of letters is not typewriter, as is commonly believed: teetertotter is longer, though it is sometimes hyphenated and in Great Britain is known as a see-saw. The longest words typable by alternating left and right hands are antiskepticism and leucocytozoans respectively.
The longest word with the vowels in order is abstemiously.