Floccinaucinihilipilification, the declaration of an item being useless, is the longest non-medical term in the English language.
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Longest officially recognized place name is Taumatawhakatangihangakoauauotamateapokaiwhenuakitanatahu.
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Switching letters is called spoonerism. For example, saying "jag of Flapan", instead of "flag of Japan".
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Anuptaphobia is the fear of staying single.
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