darnu adrnu dranu rdanu ardnu radnu danru adnru dnaru ndaru andru nadru drnau rdnau dnrau ndrau rndau nrdau arndu randu anrdu nardu rnadu nradu darun adrun draun rdaun ardun radun daurn adurn duarn udarn audrn uadrn druan rduan duran udran rudan urdan arudn raudn aurdn uardn ruadn uradn danur adnur dnaur ndaur andur nadur daunr adunr duanr udanr audnr uadnr dnuar nduar dunar udnar nudar undar anudr naudr aundr uandr nuadr unadr drnua rdnua dnrua ndrua rndua nrdua druna rduna durna udrna rudna urdna dnura ndura dunra udnra nudra undra rnuda nruda runda urnda nurda unrda arnud ranud anrud narud rnaud nraud arund raund aurnd uarnd ruand urand anurd naurd aunrd uanrd nuard unard rnuad nruad runad urnad nurad unrad
Note: these 'words' (valid or invalid) are all the permutations of the word darnu. These words are obtained by scrambling the letters in darnu.