http://en.wikipedia.org/wiki/Longest_word_in_English
The identity of the longest word in English depends upon the definition of what constitutes a "word" in the English language, as well as how "length" should be compared. In addition to words derived naturally from the language's roots (without any known intentional invention), English allows new words to be formed by coinage and construction; place names may be considered words; technical terms may be arbitrarily long. Length may be understood in terms of orthography and number of written letters, or (less commonly) phonology and the number of phonemes.
| Word | Letters | Characteristics | Dispute |
|---|---|---|---|
| Methionylthreonylthreonyl...isoleucine | 189,819 | Chemical name of the largest known protein | Technical; not in dictionary; disputed whether it is a word |
| Lopado...pterygon | 183 | Longest word coined by a major author[1] | Coined; not in dictionary; Greek transliteration |
| Pneumonoultramicroscopicsilicovolcanoconiosis | 45 | Longest word in a major dictionary[2] | Technical; coined to be the longest word |
| Pseudopseudohypoparathyroidism | 30 | Longest non-coined word in a major dictionary[3] | Technical |
| Floccinaucinihilipilification | 29 | Longest nontechnical word | Coined |
| Antidisestablishmentarianism | 28 | Longest non-coined and nontechnical word | |
| Honorificabilitudinitatibus | 27 | Longest word in Shakespeare's works |
