thens htens tehns ethns hetns ehtns thnes htnes tnhes nthes hntes nhtes tenhs etnhs tnehs ntehs enths neths hents ehnts hnets nhets enhts nehts thesn htesn tehsn ethsn hetsn ehtsn thsen htsen tshen sthen hsten shten teshn etshn tsehn stehn esthn sethn hestn ehstn hsetn shetn eshtn sehtn thnse htnse tnhse nthse hntse nhtse thsne htsne tshne sthne hstne shtne tnshe ntshe tsnhe stnhe nsthe snthe hnste nhste hsnte shnte nshte snhte tensh etnsh tnesh ntesh entsh netsh tesnh etsnh tsenh stenh estnh setnh tnseh ntseh tsneh stneh nsteh snteh ensth nesth esnth senth nseth sneth henst ehnst hnest nhest enhst nehst hesnt ehsnt hsent shent eshnt sehnt hnset nhset hsnet shnet nshet snhet ensht nesht esnht senht nseht sneht
Note: these 'words' (valid or invalid) are all the permutations of the word thens. These words are obtained by scrambling the letters in thens.