TYPEWRITER
10 letters
The longest common English word you can make from the top line of your keyboard or qwertyuiop is typewriter (10 letters).The longest possible word is rupturewort, a type of plant (11 letters).The longest slang word using all letters only once is wipeout (7 letters). The longest formal words have six letters : equity, poetry, purity, pyrite, torque, troupe and qwerty (it means the kind of keyboard we are now using).
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The longest English words you can make using only those letters are five-letter words: badge, cadge, caged, decaf, faced, fadge
Using the letters abcdefg you can spell a few 5 letter words. Badge, caged and faced are words spelled using the letters abcdefg.
There are 699 possible words, so I'm only including the longest ones:unroasteddauntersoutdaresoutearnsoutreadsreadoutsrotundasroundesttonsuredtransudeunsorteduntreadsarenousarousedastoundasunderatonersdanseurdaunterdetoursdonatesdourestendurosnaturednaturesoutdareoutearnoutreadreadoutredoutsresoundroastedrodentsrondeaurotundaroustedsanterosantoursauntersenatorsnortedsnoutedsoundersoutanestandertenourstonsuretorsadetreasontundrasundoersundrestunratedunsateduntreadadoresadornsandrosanodesantresardentaroundarousearsenoasternatonedatoneratonesautoeddatersdauntsdenarsderatsdetourdonatedonutsdotersdourasdouserdronesdusterenduronaturenestornotersnudestnursedoatersoratedoratesoreadsornateosetraoustedousteroutersoutranradonsrantedreasonredansredonsredoutrodentrotundrouensroundsrousedroutedroutesrudestrustedsandersantursarodesautedsenorasnaredsnoredsoaredsondersornedsortedsoudansouredsouterstanedstaredsternastonedstonerstoredstoundstourestrandstrodestroudsundaesundertauonstendustenorstenourtensortonerstouredtousedtradestreadstrendstronastronestundratunersturnedundoerundoesunreadunrestunseatuntroduratesuredos