The longest word

The longest official word ever (1,913 letters) is the term for the formula C1289H2051N343O375S8

Methionylglutaminylarginyltyrosylglutamylserylleucylphenyl-
alanylalanylglutaminylleucyllysylglutamylarginyllysyglutamyl-
gycylalanylphenylalanylvalylprolylphenylalanylvalylthreonyl-
leucylglycylaspartylprolylglycyllisoleucylglutamylglutaminyl-
serylleucyllysylisoleucylaspartylthreonylleucylisoleucyl-
glutamylalanylglycylalanylaspartylalanylleucylglutamylleucyl-
glycylisoleucylprolylphenylalanylserylaspartylprolylleucyl-
alanylaspartylglycylprolylthreonylisoleucylglutaminylasparaginyl-
alanylthreonylleucylarginylalanylphenylalanylalanylalanyl-
glycylvalylthreonylprolylalanylglutaminylcysteinylphenylalanyl-
glutamylmethionylleucylalanylleucylisoleucylarginylglutaminyl-
lysylhistidylprolylthreonylisoleucylprolylisoleucylglycylleucyl-
leucylmethionyltyrosylalanylasparaginylleucylvalylphenylalanyl-
asparaginyllysylglycylisoleucylaspartylglutamylphenylalanyl-
tyrosylalanylglutaminylcysteinylglutamyllysylvalylglycylvalyl-
aspartylsrylvalylleucylvalylalanylaspartylvalylprolylvalyl-
glutaminylglutamylserylalanylprolylphenylalanylarginylglutaminyl-
alanylalanylleucylarginylhistidylasparaginylvalylalanyl-
prolylisoleucylphenylalanylisoleucylcysteinylprolylprolylaspartyl-
alanylaspartylaspartylaspartylleucylleucylarginylglutaminyl-
isoleucylalanylseryltyrosylglycylarginylglycyltyrosylthreonyl-
tyrosylleucylleucylserylarginylalanylglycylvalylthreonylglycyl-
alanylglutamylasparaginylarginylalanylalanylleucylleucyllysyl-
glutamyltyrosylasparaginylalanylalanylprolylprolylleucylglutaminyl-
glycylphenylalanylglysylisoleucylserylalanylprolylaspartylglutaminyl-
valyllysylalanylalanylisoleucylaspartylalanylglycylalanylalanyl-
glycylalanylisoleucylserylglycylserylalanylisoleucylvalyllysylisoleucyl-
isoleucylglutamylglutaminylhistidylasparaginylisoleucylglutamyl-
prolylglutamyllysylmethionylleucylalanylalanylleucyllysylvalylphenyl-
alanylvalylglutaminylprolylmethionyllysylalanylalanylthreonylarginy-
lserine.

http://www.bbc.co.uk/dna/h2g2/alabaster/A182765

On the flip side, the word for categorizing something as worthless, is floccinaucinihilipilification.