Is this the longest word in the English language?
acetylseryltyrosylserylisoleucylthreonylserylprolylseryl-
glutaminylphenylalanylvalylphenylalanylleucylserylseryl-
valyltryptophylalanylaspartylprolylisoleucylglutamyl-
leucylleucylasparaginylvalylcysteinylthreonylserylseryl-
leucylglycylasparaginylglutaminylphenylalanylglutami-
nylthreonylglutaminylglutaminylalanylarginylthreo-
nylthreonylglutaminylvalylglutaminylglutaminylpheny-
lalanylserylglutaminylvalyltryptophyllysylprolylphenyla-
lanylprolylglutaminylserylthreonylvalylarginylphenylala-
nylprolylglycylaspartylvalyltyrosyllysylvalyltyrosylargin-
yltyrosylasparaginylalanylvalylleucylaspartylprolylleucyli-
soleucylthreonylalanylleucylleucylglycylthreonylphenyla-
lanylaspartylthreonylarginylasparaginylarginylisoleucyli-
soleucylglutamylvalylglutamylasparaginylglutaminylglu-
taminylserylprolylthreonylthreonylalanylglutamylthreo-
nylleucylaspartylalanylthreonylarginylarginylvalylaspar-
tylaspartylalanylthreonylvalylalanylisoleucylarginylsery-
lalanylasparaginylisoleucylasparaginylleucylvalylasparagi-
nylglutamylleucylvalylarginylglycylthreonylglycylleucyl-
tyrosylasparaginylglutaminylasparaginylthreonylphenyla-
lanylglutamylserylmethionylserylglycylleucylvalyltrypto-
phylthreonylserylalanylprolylalanylserine
At 1,185 letter long, Sam Kean, the author of "The Disappearing Spoon: And Other True Tales of Madness, Love, and the History of the World from the Periodic Table of the Elements" says it very well may be the longest word found in an English-language document not written for the specific purpose of setting the record.
The word, according to NPR, comes from virus-hunting scientists, and was published in the 1964 resource for chemists, "Chemical Abstracts." Specifically, it refers to a protein found in the tobacco mosaic virus (represented by C:785, H:1220, N:212, O:248S2).
However, this still isn't necessarily the longest word in the English language. Kean also says that he also found a tryptophan protein that runs 1,913 letters. However, that word was not published (many long molecules are simply written out by their chemical formulas), likely giving the tobacco protein the crown, as it snuck into print before scientists began adopting the shorter form, according to NPR.
While the definition of a word reamins a point of contention (some argue that a long word created for the sole purpose of setting a record is still a word), the tobacco protein is still a tremendous feat for print, according to NPR. According to Kean, scientists abandoned printing the technical names of molecules like this, because of the amount of paper used.