The longest “real” (as in non-technical) word in the English language/dictionary is flocci­nauci­nihili­pili­fication.

Anything else is either a “pseudo-word” or a technical term (more specifically, a word that was pretty much made up for a particular cause/item).

acetylseryltyrosylserylisoleucylthreonylserylprolylserylglutaminyl- phenylalanylvalylphenylalanylleucylserylserylvalyltryptophylalanyl- aspartylprolylisoleucylglutamylleucylleucylasparaginylvalylcysteinyl- threonylserylserylleucylglycylasparaginylglutaminylphenylalanyl- glutaminylthreonylglutaminylglutaminylalanylarginylthreonylthreonyl- glutaminylvalylglutaminylglutaminylphenylalanylserylglutaminylvalyl- tryptophyllysylprolylphenylalanylprolylglutaminylserylthreonylvalyl- arginylphenylalanylprolylglycylaspartylvalyltyrosyllysylvalyltyrosyl- arginyltyrosylasparaginylalanylvalylleucylaspartylprolylleucylisoleucyl- threonylalanylleucylleucylglycylthreonylphenylalanylaspartylthreonyl- arginylasparaginylarginylisoleucylisoleucylglutamylvalylglutamyl- asparaginylglutaminylglutaminylserylprolylthreonylthreonylalanylglutamyl- threonylleucylaspartylalanylthreonylarginylarginylvalylaspartylaspartyl- alanylthreonylvalylalanylisoleucylarginylserylalanylasparaginylisoleucyl- asparaginylleucylvalylasparaginylglutamylleucylvalylarginylglycyl- threonylglycylleucyltyrosylasparaginylglutaminylasparaginylthreonyl- phenylalanylglutamylserylmethionylserylglycylleucylvalyltryptophyl- threonylserylalanylprolylalanylserine

This 1185-letter “word” is the chemical name for “Coat Protein, Tobacco Mosaic Virus, Dahlemense Strain”. It is supposedly the longest word in the English language.

The name on the sign that marks this hill is ‘Taumatawhakatangihangakoauauotamateaturipukakapikimaungahoronukupokaiwhenuakitanatahu’, which translates roughly as The summit where Tamatea, the man with the big knees, the climber of mountains, the land-swallower who travelled about, played his flute to his loved one. At 85 letters, it is one of the longest placenames in the world.

Pneumonoultramicroscopicsilicovolcanoconiosis, 45 letters, longest word in any of the major English language dictionaries including the OED

According to wikipedia…

The longest word in English depends upon the definition of what constitutes an English word.

– There is a word that is 1185 letters! However, it’s technical.

– 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.

– Oxford English Dictionary contains pseudopseudohypoparathyroidism (30 letters).

– 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.

Check out the article! http://en.wikipedia.org/wiki/Longest_word_in_English

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 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.[1]

The Oxford English Dictionary contains pseudopseudohypoparathyroidism (30 letters).

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.[2][3][4][5]

First (for alwaysmoose) try something a little bit longer than a mile — can you say: “light-year” — that’s the distance light travels in a year, about 5.88 trillion miles (or 9.46 trillion km).

or, at 74 letters:

“Twoallbeefpattiesspecialsaucelettucecheesepicklesonionionsonasesameseedbun”

In case you didn’t recognize it, that’s: “Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.” — a trademarked slogan first used by McDonald’s in 1975. The saying has remained popular even though it is not in “official use” by McDonald’s. Although shown above properly punctuated, it was often spoken rapidly in ads as a single word. The original jingle was written and performed by Mark Vieha, purposely turning the ingredients into a tongue twister. It first appeared in a TV commercial titled “In a Word” created by Dan Nichols and his team at Needham Harper and Steers, Chicago.

or, what about this one at 100 letters:

“Lipsmackinthirstquenchinacetastinmotivatingoodbuzzincooltalkinhighwalkinfastlivinevergivincoolfizzin”

In 1973, Pepsi’s advertising agency Boase Massimi Pollitt used a 100-letter but several-word term for Pepsi: “Lipsmackin’ thirstquenchin’ acetastin’ motivatin’ goodbuzzin’ cooltalkin’ highwalkin’ fastlivin’ evergivin’ coolfizzin’.” used in TV and film advertising.

Here’s a hyperlink to an old Pepsi ad to show you:

( http://www.adslogans.co.uk/hof/IH002467.html )

pneumonoultramicroscopicsilicovolcanoconiosis

It used to be the longest word. I dont know if it still is. It is some sort of lung disorder

Lopadotemachoselachogal,

eokranioleipsanodrimhypotr,

immatosilphio-paraomelitoka,

takechymenoki,

chlepikossyphophattop,

eristeralektryonop-

tekephallio

kigklopeleiol,

agoiosiraiobaphetr

aganopterygon.

a word of 183 letters that describes a dish by stringing together its ingredients.

Acetylseryltyrosylserylisoleucylthreonylserylprolylserylglutaminyl

1185 letters

Smiles. Theres a mile between the s’s

I always thought it was antidisestablishmenttarianism.