Smiles--because there's a mile between both S'es.

The full name of the tryptophan synthetase A protein, an enzyme with 267 amino acids, extends to 1,913 letters:
methionylglutaminylarginyltyrosylglutamylserylleucylphenylalanyla lanylglutaminylleucyllysylglutamylarginyllysylglutamylglycylalany lphenylalanylvalylprolylphenylalanylvalylthreonylleucylglycylaspa rtylprolylglycylisoleucylglutamylglutaminylserylleucyllysylisoleu cylaspartylthreonylleucylisoleucylglutamylalanylglycylalanylaspar tylalanylleucylglutamylleucylglycylisoleucylprolylphenylalanylser ylaspartylprolylleucylalanylaspartylglycylprolylthreonyliso leucylglutaminylaspfraginylalanylthreonylleucylarginylalanylpheny lalanylalanylalanylglycylvalylthreonylprolylalanylglutaminylcyste inylphenylalanylglutamylmethionylleucylalanylleucylisoleucylargin ylglutaminyllysylhistidylprolylthreonylisoleucylprolylisoleucylgl ycylleucylleucylmethionyltyrosylalanylasparaginylleucylvalylpheny lalanylasparaginyllysylglycylisoleucylaspartylglutamylphenylalany ltyrosylalanylglutaminylcysteinylglutamyllysylvalylglycylva lylaspartylserylvalylleucylvalylalanylaspartylvalylprolylvalylglu taminylglutamylserylalanylprolylphenylalanylarginylglutaminylalan ylalanylleucylarginylhistidylasparaginylvalylalanylprolylisoleucy lphenylalanylisoleucylcysteinylprolylprolylaspartylalanylaspartyl aspartylaspartylleucylleucylarginylglutaminylisoleucylalanylseryl tyrosylglycylarginylglycyltyrosylthreonyltyrosylleucylleucylseryl arginylalanylglycylvalylthreonylglycylalanylglutamylasparag inylarginylalany...

There is a debate about the longest word in the English language; in my opinion it's floccinaucinihilipilificatious compared to the debate on antidisestablishmentarianism. Those with hippopotomonstrosesquippedaliophobia tend to avoid the subject. The longest word in the common English dictionary is pneumohoultramicroscopicsilicovolcanoko niosis, although in medical diaries and such methionylglutaminylarginyltyrosylglutam ylserylleucylphenylalanylalanylglutamin ylleucyllysylglutamylarginyllysylglutam ylglycylalanylphenylalanylvalylprolylph enylalanylvalylthreonylleucylglycylaspa rtylprolylglycylisoleucylglutamylglutam inylserylleucyllysylisoleucylaspartylth reonylleucylisoleucylglutamylalanylglyc ylalanylaspartylalanylleucylglutamylleu cylglycylisoleucylprolylphenylalanylser ylaspartylprolylleucylalanylaspartylgly cylprolylthreonylisoleucylglutaminylasp fraginylalanylthreonylleucylarginylalan ylphenylalanylalanylalanylglycylvalylth reonylprolylalanylglutaminylcysteinylph enylalanylglutamylmethionylleucylalanyl leucylisoleucylarginylglutaminyllysylhi stidylprolylthreoylisoleucylprolylisole ucylglycylleucylleucylmethionyltyrosyla lanylasparaginylleucylvalylphenylalanyl asparaginyllysylglycylisoleucylaspartyl glutamylphenylalanyltyrosylalanylglutam inylcysteinylglutamyllysylvalylglycylva lylaspartylserylvalylleucylvalylalanyla spartylvalylproly...

The longest word in the English language according to Guinness is FLOCCINAUCINIHILIPILIFICATION. The lung disease one is the longest unnofficial word, cos it's a compound scientific term, and it's possible to make sceintific names stupidly long, like the 1700+ character one, but that's neverbeen in a dictionary.

The longest word entered in a dictionary anywhere is Swedish, and it's NORDOSTERSJOKUSTARTILLERIFLYGSPANINGSSIMULATORANLAGG-
NINGSMATERIELUNDERHALLSUPPFOLJNINGSSYSTEMDISKUSSIONS-
INLAGGSFORBEREDELSEARBETEN, which means "preparatory work on the contribution to the discussion on the maintaining system of support of the material of the aviation survey simulator device within the north-east part of the coast artillery of the Baltic."