serif esrif sreif rseif ersif resif seirf esirf sierf iserf eisrf iesrf srief rsief siref isref risef irsef erisf reisf eirsf iersf riesf iresf serfi esrfi srefi rsefi ersfi resfi sefri esfri sferi fseri efsri fesri srfei rsfei sfrei fsrei rfsei frsei erfsi refsi efrsi fersi rfesi fresi seifr esifr siefr isefr eisfr iesfr sefir esfir sfeir fseir efsir fesir sifer isfer sfier fsier ifser fiser eifsr iefsr efisr feisr ifesr fiesr srife rsife sirfe isrfe risfe irsfe srfie rsfie sfrie fsrie rfsie frsie sifre isfre sfire fsire ifsre fisre rifse irfse rfise frise ifrse firse erifs reifs eirfs ierfs riefs irefs erfis refis efris feris rfeis freis eifrs iefrs efirs feirs ifers fiers rifes irfes rfies fries ifres fires
Note: these 'words' (valid or invalid) are all the permutations of the word serif. These words are obtained by scrambling the letters in serif.