We’ve had threads about the longest word in the English language, but what is the longest word in ***any ***language, excluding proper nouns?
And while we’re at it, what is the longest proper noun in any language?
Ooh, I know this one. Or at least, I think I can hazard a guess:
Llanfairpwllgwyngyllgogerychwyrndrobwll Llantysiliogogogoch is the name of a Welsh village. It means “St Mary’s church in the hollow of the white hazel near a rapid whirlpool and the Church of St Tysilio of the red cave” in Welsh.
panache45: Does this word need to be in a dictionary, or can nonce words and hapax legomena be considered as well? Of course, the concept of a word is somewhat language-dependent. We English-speakers are pleased to call sesquipedalian Greco-Latin terms constructed from roots ‘words’ but we might not be so inclusive when it comes to terms that carry the full meaning of a sentence constructed in agglutinative languages such as Chukchi.
As for the longest proper noun, it’s probably the proper name of some absurdly complex chemical constructed (both the word and the chemical) from rafts and rafts of simpler particles.
Nordostersjokustartilleriflygspaningssimulatoranlaggningsmaterielunderhallsuppfoljningssystemdiskussionsinlaggsforberedelsearbeten is Swedish for:
Preparatory work on the contribution to the discussion on the maintaining system of support of the material of the aviation survey simulator device within the north-east part of the coast artillery of the Baltic.
That one might be a bit of a cheat, actually.
(I’m still pleased to have an old photograph of me in front of the railway station sign though.) 
Apparently, Thailand beats Wales into a cocked hat.
*“Bangkok is a city of extremes and superlatives, a city you do not react to indifferently,” says Thailand at a Glance. "Recently declared the world’s hottest city by the World Meteorological Organization, it also boasts the world’s longest name:
Krung-thep-maha-nakorn-boworn-ratana-kosin-mahintar- ayudhya-amaha-dilok-pop-nopa-ratana-rajthani-burirom-udom-rajniwes-mahasat-arn-amorn-pimarn- avatar-satit- sakattiya-visanukam.
“Not surprisingly, only a handful of Thais can remember such a mouthful, although the abbreviated translation of the whole is a relatively brief Jewelled city of the god Indra. However, most Thais simply refer to it as Krung Thep, City Angels.”
We sought a ruling from a Bangkok wordsmith, Theppitak Karoonboonyanan who said the correct spelling (163 letters) is
Krungthepmahanakornamornratanakosinmahintarayutthayamahadilokphop
nopparatrajathaniburiromudomrajaniwesmahasatharn
amornphimarnavatarnsathitsakkattiyavisanukamprasit.
Theppitak separated the words of K161t and translated them as:
krungthep mahanakorn
The great city of angels,
amorn rattanakosin mahintara yutthaya mahadilok phop
the supreme unconqueralble land of the great immortal divinity (Indra),
noparat rajathani burirom
the royal capital of nine noble gems, the pleasant city,
udomrajaniwes mahasatharn
with plenty of grand royal palaces,
amorn phimarn avatarnsathit
and divine paradises for the reincarnated deity (Vishnu),
sakkatattiya visanukam prasit
given by Indra and created by the god of crafting (Visnukarma).*
Scientific names always throw this type of concentration. If you took, say, a protein and tried to give it a chemical name using IUPAC rules, it’d probably go on for a few pages.
Competition. Sorry - I’m really really tired right now.
Well… through a property that linguists call recursion, you can use alternating suffixes (morphemes?) to create a word just as long as you please, at least in some languages. So, “fearless” becomes “fearlessness” becomes “fearlessnessless” becomes “fearlessnesslessness,” ad infinitum, each with its own nuance of meaning. Of course, keeping track of these nuances of meaning rapidly becomes difficult in English, rendering it not terribly practical as a means of communicating. But there are other languages that are already far more productive at generating compound words (some languages combine the dozens of morphemes that represent all of the ideas in a sentence into a single word), and since this can take place on the sentence level it seems likely that speakers of one of these languages could handily surpass any proper name just in the course of everyday speech. I suppose an actual linguist (as opposed to me, who just remembers a bunch of stuff from the couple of courses he’s taken) can come along to confirm or deny that theory, but it makes sense to me.
I went and lost my german textbook a few years ago (actually, I think I forgot to pick it up after I left the exam) and have forgotten most of what I learned, but isn’t it the case that german numbers are spelled out as one long single word? If that is the case, then there clearly is no longest german word!
That Welsh village “name” might be 58 letters long but I’ve found in the Guinness Book of World Records the name of a hill in New Zealand
Taumatawhakatangihangakoauauatamateapokaiwhenuakitanatahu
which is 57 letters long and Guinness considers this the longest place name in use.
Yes, it also mentions that Thailand’s official name for its capital city is (in its most scholarly translation) is 175 letters long.
It also mentions a protein with a 1,913 letter name which I sure as heck won’t type out - for no other reason that I know someone else will post an even longer chemical name.
Oh, and of course “smiles” is the longest word in the English language.
There’s a mile between the first and last letters.
I can’t recall the exact word and will try to contact her and post it - but a German speaking friend told me once that German’s longest word was one that meant ‘the key to the door of the house of the wife of the fisherman…’ (Something resembling that but longer)
How about the longest word that isn’t a compound word?
A thing that might never be settled, but check out this page:
A Collection of Word Oddities and Trivia
http://members.aol.com/gulfhigh2/words11.html
(at the bottom, you will see links to other pages at the site - go also to pages 12 and 13)
People, people, the OP specifically said no proper nouns.
In the first half of the OP, yes. However:
I think that, without actually having a specific word to cite, there is a valid answer here. I would define “word” as “single sequence of letters, without space intervening, which has a specific meaning recognized or capable of being deciphered by a speaker of the language with the requisite training.” In other words, I expect neither a child nor a casual reader to immediately recognize, say, “umbelliferivorous” – but someone with a little background in the life science will see it as an adjective meaning “having a principal foodstuff of the umbellifer family, including Queen Anne’s Lace and related plants.” Similarly, “pseudosinotibetic” would mean "a language mimicking but not directly related to the large language group of continental eastern Asia which includes Guoyu (“Mandarin”), Cantonese, Tibetan, Burmese, etc. – and that would come clear to anyone taking the time to sort out the elements and look up what connection they might have to each other.
By this system, then, the longest meaningful word which can be constructed, interpreted by others, and have an actual legitimate referent, would be the largest, most complex protein in existence, painstakingly described in terms of its constituent organic radical constituents in careful accordance with IUPAC standards. It would probably take up several pages of fine print, but any person who has ever studied organic chemistry or who wants to bother dredging out the IUPAC nomenclature standards could read that monstrosity of a word and identify the structure of the protein from it.