tsofi stofi tosfi otsfi sotfi ostfi tsfoi stfoi tfsoi ftsoi sftoi fstoi tofsi otfsi tfosi ftosi oftsi fotsi softi osfti sfoti fsoti ofsti fosti tsoif stoif tosif otsif sotif ostif tsiof stiof tisof itsof sitof istof toisf otisf tiosf itosf oitsf iotsf soitf ositf siotf isotf oistf iostf tsfio stfio tfsio ftsio sftio fstio tsifo stifo tisfo itsfo sitfo istfo tfiso ftiso tifso itfso fitso iftso sfito fsito sifto isfto fisto ifsto tofis otfis tfois ftois oftis fotis toifs otifs tiofs itofs oitfs iotfs tfios ftios tifos itfos fitos iftos ofits foits oifts iofts fiots ifots sofit osfit sfoit fsoit ofsit fosit soift osift sioft isoft oisft iosft sfiot fsiot sifot isfot fisot ifsot ofist foist oifst iofst fiost ifost
Note: these 'words' (valid or invalid) are all the permutations of the word tsofi. These words are obtained by scrambling the letters in tsofi.