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Pneumonoultramicroscopicsilicovolcanoconiosis
Pseudopseudohypoparathyroidism
Floccinaucinihilipilification

* Strengths is the longest word in the English language containing only one vowel.
* Rhythms is the longest word in the English language containing none of the five recognised vowels.
* Schmaltzed and strengthed appear to be the longest monosyllabic words recorded in OED; but if squirrelled is pronounced as one syllable only (as permitted in SOED for squirrel), it is the longest.
* Euouae, a medieval musical term, is the longest English word consisting only of vowels, and the word with the most consecutive vowels. However, the “word” itself is simply a mnemonic consisting of the vowels to be sung in the phrase “seculorum Amen” at the end of the lesser doxology. (Although u was often used interchangeably with v, and the variant “Evovae” is occasionally used, the v in these cases would still be a vowel.)
* The longest words with no repeated letters are dermatoglyphics, misconjugatedly and uncopyrightables.[15]
* The longest word whose letters are in alphabetical order is the eight-letter Aegilops, a grass genus.
* The longest words recorded in OED with each vowel only once, and in order, are abstemiously, affectiously, and tragediously (OED). Fracedinously and gravedinously (constructed from adjectives in OED) have thirteen letters; Gadspreciously, constructed from Gadsprecious (in OED), has fourteen letters. Facetiously is among the few other words directly attested in OED with single occurrences of all five vowels and the semivowel y.