In Language on Vacation (Scribner's, 1965), Dmitri Borgmann devotes several pages to a survey of the longest words in the English language. As might be expected, he finds it necessary to proceed from standard reference works such as the Webster dictionaries to ever-more-esoteric sources as the word-length is increased. One rapidly enters the realm of the nonce word -- a word used but once, or at most a few times by a single author. Since Borgmann's book appeared, it has become apparent to logologists that chemical names describing complex organic compounds can be almost infinitely expanded; the Guiness Book of Records cites a 1913-letter chemical term which earlier (May 1968) was published in Word Ways. Yet, it is again likely that one is entering the realm of the nonce word; in writing about a compound, a chemist is more likely to refer to it by formula if the name is at all long.
Eckler, A. Ross
"The Longest Dictionary Words,"
Word Ways: Vol. 5
, Article 7.
Available at: http://digitalcommons.butler.edu/wordways/vol5/iss2/7