You’d imagine that’s an easy question, wouldn’t you? Which word has more letters than any other? Done!
Well, you’d think so, but this is a surprisingly debated question.
One candidate for the title of longest word is methionyl…isoleucine, at 189,819 letters. This is the chemical name for titin, the largest-known protein. This word’s claim though, is disputed. Firstly, because it’s a technical term, not used in everyday language (and probably not much within the world of chemistry either, when you can just say titin).
And also, because this word was created using the naming guidelines of the International Union of Pure and Applied Chemistry. This naming system is based on the structure of chemical compounds, and while logical and reliable, it can lead to incredibly long names, not suitable for either writing or speaking.
What about the 45-letter pneumonoultramicroscopicsilicovolcanoconiosis, a word coined as an alternative to silicosis, a disease caused by inhaling silica dust? It’s the longest word to appear in a dictionary (first appearing in the 1939 supplement of the Merriam-Webster New International Dictionary, 2nd Edition). That gives it a little more legitimacy, but it’s still generally discounted because it’s a technical term, and also because it was created as a deliberately absurd word by Everett M. Smith, president of the National Puzzlers’ League.
Contrived coinage like this also rules out supercalifragilisticexpialidocious (34 letters), famously from Mary Poppins, and floccinaucinihilipilification (29 letters), which was deliberately created as a joke, with each root roughly meaning nothing.
Antidisestablishmentarianism (28) is often cited as the longest word, but is still not accepted by all dictionaries due to its lack of usage. It’s also an example of agglutinative construction: the creation of new words via the addition of suffixes and prefixes. Such words are often not accepted because they could really be infinite in length. Imagine, for example, that you’re opposed to antidisestablishmentarianism. Then you’d be anti-antidisestablishmentarianism. And if your friend were opposed to your position, then, well, you can see how we could end up with an infinite series of prefixes.
If we consider actual usage to be important, then deinstitutionalization and counterrevolutionaries (both 22) have been judged by statistician A. Ross Eckler Jr. to be the longest words likely to be encountered in general text.
A computer study analysing a huge number of genuine English texts found that uncharacteristically (20) is the longest word someone’s likely to encounter on an everyday basis.
So yes, it’s quite hard to really figure out what the longest word is, because, when you get right down to it, what precisely is a word? If we’re liberal about the definition it’s really any combination of letters that’s used by even one person just once as part of the English language.
But then there could be a basically infinite number of possible words, of infinite possible lengths. So usage is generally considered an important factor in deciding the longest word. But then how do you really define frequently-used in this regard? And doesn’t that get us into the murky waters of deciding whether some words are more legitimate than others? Sure, it might be impractical to use a word with 189,819 letters, but it’s still a word, created using perfectly legitimate methods for coining words.
Perhaps the most logical thing to do is simply to not try to figure out which is the longest word. But then, that’d really just be trying to suppress our instinct to rank things, wouldn’t it?