Largest word in Enlish

1. pneumonoultramicroscopicsilicovolcanoconiosis - 45 letters
*description - a factitious word alleged to mean 'a lung disease caused by the inhalation of very fine silica dust causing inflammation in the lungs.

2. floccinaucinihilipilification - 29 letters
* description - the act of describing something as worthless, or making something to be worthless by deprecation

3. antidisestablishmentarianism - 28 letters
* meaning - opposition to the belief that there should not be an official relationship between a country's government and its national church

4. Methionylglutaminylarginytyrosylglutamylseryll
eucylphenylalanylalanylglutaminyll-eucyllysylglut
amylarginyllysylglutamylglycylalanylphenylalanyv
alylprolylphenylalanyl-valythreonylleucylglycylas
partylprolyglycylisoleucylglutamylglutaminylsery
lleucyllysyl-isoleucylaspartylthreonylleucylisoleuc
ylglutamylalanylglycylalanylaspartylalanylleucy-
lglutamylleucylglycylglycylisoleucylprolylpheny
lalanylserylaspartylprolylleucelalanyla-spartygly
cylprolythreonylisoleucylglutamiylasparaginyla
lanylthreonylleucylarginylala-nylphenylalanyla
lanylglycylvalyltheonylprolylalanylglutaminyl
cysteinylphenylalanygll-utamylmethionylleuc
yalanylleucylisoleucylarginylglutaminyllysylh
istidylprolylthreonyl-isoleucylpriIylisoleucylg
lycylleucylleucylmethionyltyrosylalanylaspa
raginylleucylvalyp-henylalanylasparaginylly
sylgyycylisoleucylaspartylglutamylphenyla
lanyltyrosylalanyl-gutaminyllcysteinylgluta
myllysylvalylglycylavlylaspartylserylvalyll
eucylvalylalanylasp-artylvalyprolylvalylglu
taminylglutamyllserylalanyprolyphenylala
nylarginylglutaminylal-anylalanylleucylarg
inylhistidylasparaginylvaylalanylprolylisol
eucylphenylalanylisoleu-cylcysteinylproly
lprolylaspartylalanylaspartylaspartylaspart
ylleucylleucylarginyglutam-inylisoleucyla
lanyylseryltyrosylglycylarginylglycyltyrosy
lthreonyltyrosylleucylleucylser-ylarginyla
lanylglycylvalythreonylglycylalanylglutam
ylasparaginylarginylanylalanylleu-cylproly
lleucylaspaaginylhistidylleucylvaylalanylly
sylleucyllysylglutamyltyrosylasarag-inylgl
ycylphenylalanylglycylisoleucylalanylprol
ylaspartylglutaminylvalyllysylalanylala-ny
lisoleucylaspartylalanylalanyglycylalanyla
lanyglycylalanylisoleucylserylglycyseryla-
lanylisoleucylbalyllsylisoleucylisoleucylg
lutamyyylglutaminylhistidylasparaginylis
ole-ucylglutamylprolyglutamyllysylmethi
onylleucylalanylalanylleucyllysylvalylph
enylalaby-lvalylglutaminlylprolylmethion
yllysylalanylalanylthreonylarginylserine

* description- "Scientific name for Trypthophan synthetase (that is a protien with 267 amino acids) (1 909 letters)

* Debates are still active on this topic (The largest word in English). it is said that there is a word 189,819 letters long. It is titin, a protein that is important in the contraction of striated muscle tissues. But of no use, who is going to use it..

* floccinaucinihilipilification -

With 29 letters, is the longest non-technical word in the first edition of the Oxford English Dictionary (OED), which presents it as "enumerated in a well-known rule from the Eton Latin Grammar". The OED dates its first use in literature at 1741 in William Shenstone's Works in Prose and Verse: "I loved him for nothing so much as his flocci-nauci-nihili-pili-fication of money".

• flocci facere (from floccus, -i a wisp or piece of wool)
• nauci facere (from naucum, -i a trifle)
• nihili facere (from nihil, -i nothing; something valueless (lit. "not even a thread" from ni+hilum))
• pili facere (from pilus, -i a hair; a bit or a whit; something small and insignificant)