To figure out what is the longest word, we need to ask ourselves first what a “real” word is. In scientific usage, you can give chemicals names hundreds or even thousands of letters long by stringing together all sorts of word parts. Also, at least in theory, just as you could have an anti-missile, you could have an anti-anti-missile, an anti-anti-anti-missile and so on, and again come up with an arbitrarily long word.
So, it might be better to ask, what’s the longest word in a recognized dictionary? To that, the answer is fairly simple: pneumonoultramicroscopicsilicovolcanoconiosis, a 45-letter word for a lung disease that is listed in Webster’s New Millennium Dictionary of English, the Random House Dictionary and Merriam-Webster’s Medical Dictionary.
That word isn’t listed in all dictionaries, however. The longest word in the first edition of the Oxford English Dictionary, which might be considered the gold standard of standard English, was the 29-letter floccinaucinihilipilification, which involves estimating something as worthless.
Neither of those words, however, are used much in real life (and neither is listed in the American Heritage Dictionary). Do a web search for either one, and you’ll usually find it in an article about long words rather than being used for their meaning. Perhaps the longest word that has had real use (although it is used more today as an example of a long word) is antidisestablishmentarianism, which at 28 letters referred to the political belief opposing the elimination of the Church of England as the official church.
Incidentally, determining what is a real word also makes it difficult to give a clear designation of the longest words in other languages as well. But one designation for the longest word in Spanish is a word that has real-life use: electroencefalografistas, referring to medical professionals who operate a brain-monitoring machine.
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