What is the longest word ever in the English language?

Answer 1

pneumono­ultra­micro­scopic­silico­volcano­coniosis (45 letters)

... it is the name of a lung disease caused by inhaling fine silica dust.

other long words are:

pseudopseudohypoparathyroidism (30 letters).

flocci­nauci­nihili­pili­fication (29 letters) = "the act of estimating something as worthless"

anti­dis­establishment­arianism

Answer 2

The word with the most letters is a name of protein, as a name, it technically does not qualify as a word, but at 1913 characters, we just had to include it. Theoretically these names can contain an infinite amount of characters, but this one qualifies as it has actually been used in a medical journal.

methionylglutaminylarginyltyrosylglutamylserylleucyl phenylalanylalanylglutaminylleucyllysylglutamylarginyl lysylglutamylglycylalanylphenylalanylvalylprolylphenyl alanylvalylthreonylleucylglycylaspartylprolylglycylisol eucylglutamylglutaminylserylleucyllysylisoleucylaspartyl threonylleucylisoleucylglutamylalanylglycylalanylaspartyl alanylleucylglutamylleucylglycylisoleucylprolylphenyl alanylserylaspartylprolylleucylalanylaspartylglycylprolyl threonylisoleucylglutaminylasparaginylalanylthreonylleucyl arginylalanylphenylalanylalanylalanylglycylvalylthreonyl prolylalanylglutaminylcysteinylphenylalanylglutamyl methionylleucylalanylleucylisoleucylarginylglutaminyllysyl histidylprolylthreonylisoleucylprolylisoleucylglycylleucyl leucylmethionyltyrosylalanylasparaginylleucylvalylphenyl alanylasparaginyllysylglycylisoleucylaspartylglutamylphenyl alanyltyrosylalanylglutaminylcysteinylglutamyllysylvalyl glycylvalylaspartylserylvalylleucylvalylalanylaspartylvalyl prolylvalylglutaminylglutamylserylalanylprolylphenylalanyl arginylglutaminylalanylalanylleucylarginylhistidylasparaginyl valylalanylprolylisoleucylphenylalanylisoleucylcysteinyl prolylprolylaspartylalanylaspartylaspartylaspartylleucyl leucylarginylglutaminylisoleucylalanylseryltyrosylglycyl arginylglycyltyrosylthreonyltyrosylleucylleucylserylarginyl alanylglycylvalylthreonylglycylalanylglutamylasparaginyl arginylalanylalanylleucylprolylleucylasparaginylhistidyl leucylvalylalanyllysylleucyllysylglutamyltyrosylasparaginyl alanylalanylprolylprolylleucylglutaminylglycylphenylalanyl glycylisoleucylserylalanylprolylaspartylglutaminylvalyllysyl alanylalanylisoleucylaspartylalanylglycylalanylalanylglycyl alanylisoleucylserylglycylserylalanylisoleucylvalyllysylisol eucylisoleucylglutamylglutaminylhistidylasparaginylisoleucyl glutamylprolylglutamyllysylmethionylleucylalanylalanylleucyl lysylvalylphenylalanylvalylglutaminylprolylmethionyllysyl alanylalanylthreonylarginylserine

Answer 3

The word FLOCCINAUCINIHILIPILIFICATION (29 letters), meaning an estimation of something as worthless. Supposedly the real longest word in the English language, according to Oxford English Dictionary.

Answer 4

Antidisestablishmentarianisms.

Answer 5

Masospectographicisotopicdoublediafanadiathermascope...
pronounced:
Masso specto graphic isotope ik double dya fawna dya therma scope

Answer 6

Looooooooooooooooong ;-)