The longest word in English is ________.

antidisestablishmentterism

I think smiles

if you have learned university biology, you will find there never can be a longest word in English, let me give you an example:
methionylglutaminylarginyltyrosylglutamylserylleucylphenylalanylalanyl-

glutaminylleucyllysylglutamylarginyllysylglutamylglycylalanylphenylalanylvalyl-

prolyphenylalanylvalythreonylleucylglycylaspartylprolylglycylisoleucyl-

glutamylglutaminylserylleucyllysylisoleucylaspartylthreonylleucylisoleucyl-

glutamylalanylglycylalanylasparthlalanylleucylglutamylleucylglycylisoleucylprolyl-

phenylalanylserylaspartylprolylleucylalanylaspartylglycylprolylthreonylisoleucyl-

glutaminylaspfraginylalanylthreonylleucylarfinylalanylphenylalanylalanylalanyl-

glycylvalythreonylprolylalanylglutaminylcysteinylphenylalanylglutamylmethionylleu-

cylalanylleuoylisoleucylarginylglutaminyllysyhistidylprolylthreonylisoleucylprolyli-

soleucylglycylleucylmethionyltyrosylalanylasparaginylleucylvalylphenylalany-

lasparaginyllysyglycylisoleucylaspartylglutamylphenylalanylthrosylalanyl-

glutaminylcysteinylglutamyllysylvalylglycylvalylaspartylserylvalylleucylval-

ylalnylaspartylvalylprolylvalylglutaminylglutamylserylalanylprolylphenylalanylarginyl-

glutaminylalanylalanylleucylarginylhistidylasparaginyvalylalanylprolylisoleucyl-

prolylisoleucylphenylalanylisoleucylphenylalanylisoleucylcysteinylprolylproly-

laspartylalanylaspartylaspartylaspartylleucylleucylarginylglutaminylisoleucy-

lalanylseryltyrosylglycylarginylglycyltyrosylthreonyltyrosylleucylleucylsery-

larginylalanylglycylvalylthreonylglycylalanylglutamylasparainylarginylalanylalanylleucyl-

prolylleucylasparaginylhistidylleucylvalylalanyllysylleucyllysylglutamyltyrosylasparaginy-

lalanylalanylprolylprolylleucylglutaminylglgycylphenylalanylglycylisoleucylserylalanylproly-

laspartylglutaminylvalyllysylalanylalanylisoleucylaspartylalanylglycylalanylalanylgly-

cylalanylisoleucylserylglycylserylalanylisoleucylvalyllysylisoieucylisoleucylglutamyl-

glutaminylhistidylasparaginylisoleucylglutamylprolylglutamyllysylmethionylleucylalaalanylleucyllysylvalylphenylalanylcalylglutaminylprolylmethionlysylalanylalanylthreony

Black_Rose wrote:

The longest word in English is pneumonoultramicroscopicsilicovolcano-coniosis, (45 letters) meaning 'a lung disease caused by the inhalation of very fine silica dust'.  Look it up if you don't believe me!

I think this is the correct answer unless you are considering those long organic chemistry names!!