This 1185-letter "word" is the chemical name for "Coat Protein, Tobacco Mosaic Virus, Dahlemense Stain". It is supposedly the longest word in the English language.

The term was published in the American Chemical Society's Chemical Abstracts in 1972, and is considered by some to be the longest real word. It does hold the record for the longest word in an English language publication in a serious context, that is, for some reason other than to publish a very long word.

In its complete form, the 1185-letter word is:

acetylseryltyrosylserylisoleucyl-
threonylserylprolylserylglutaminyl-
phenylalanylvalylphenylalanylleucyl-
serylserylvalyltryptophylalanyl-
aspartylprolylisoleucylglutamylleucyl-
leucylasparaginylvalylcysteinyl-
threonylserylserylleucylglycyl-
asparaginylglutaminylphenylalanyl-
glutaminylthreonylglutaminylglutaminyl-
alanylarginylthreonylthreonyl-
glutaminylvalylglutaminylglutaminyl-
phenylalanylserylglutaminylvalyl-
tryptophyllysylprolylphenylalanyl-
prolylglutaminylserylthreonylvalyl-
arginylphenylalanylprolylglycylaspartyl-
valyltyrosyllysylvalyltyrosyl-
arginyltyrosylasparaginylalanylvalyl-
leucylaspartylprolylleucylisoleucyl-
threonylalanylleucylleucylglycyl-
threonylphenylalanylaspartylthreonyl-
arginylasparaginylarginylisoleucyl-
isoleucylglutamylvalylglutamyl-
asparaginylglutaminylglutaminylseryl-
prolylthreonylthreonylalanylglutamyl-
threonylleucylaspartylalanylthreonyl-
arginylarginylvalylaspartylaspartyl-
alanylthreonylvalylalanylisoleucyl-
arginylserylalanylasparaginylisoleucyl-
asparaginylleucylvalylasparaginyl-
glutamylleucylvalylarginylglycyl-
threonylglycylleucyltyrosylasparaginyl-
glutaminylasparaginylthreonyl-
phenylalanylglutamylserylmethionyl-
serylglycylleucylvalyltryptophyl-
threonylserylalanylprolylalanylserine

The letter combination yl appears in the word 166 times.