.When it comes to the longest word, there are many theories and criteria. There are debates whether to count the name of diseases (which usually are actually phrases or many words that are written without spaces, hence giving a virtual sense that the name is actually a single word), and also there are made up long words by some poet or writers. So, there has always been a debate as to what is the legal longest word. Anyways, below are some words considered longest: 1. supercalifragilisticexpialidocious: included in Oxford dictionary. 2. pneumonoultramicroscopicsilicovolcanoconiosis: included in Oxford dictionary. It means "a lung disease caused by the inhalation of very fine silica dust from volcanic eruption". Regarded by the Guiness Book of World Records as the longest made-up word. 3. floccinaucinihilipilification: It means "the estimation of something as valueless". The Guiness Book of World Records regards this as the "real" longest word in English language. But the Merriam Webster dictionary does not include this word because it believes the word is just a made-up example for a long word. 4. antidisestablishmentarianism: means "opposition to the disestablishment of the Church of England" 5. honorificabilitudinitatibus: invented by William Shapespeare in his play "Love's Labour's Lost" 6. tetramethyldiaminobenzhydrylphosphinous: a kind of acid 7. hepaticocholangiocholecystenterostomies: it is a surgical creation of a connection between the gall bladder and a hepatic duct and between the intestine and the gall bladder 8. formaldehydetetramethylamidofluorimum: a chemical compound. 9. dimethylamidophenyldimethylpyrazolone: a chemical compund 10. dichlorodiphenyltrichloroethane: long name for DDT, the poisonous chemical compound 11. Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch: It is a village in Wales, England. ************************************ My general reaction would be to not include scientific chemical compound names in the longest name book because clearly they are actually two or three different chemical names put together.