Interex or Interrex: How To spell?
The word Interex is misspelled against Interrex, a noun meaning "An interregent, or a regent."
Interrex has double "rr" is mispronounced as "r"Remember double 'RR' in between the strings inte & ex which should not be misspelled with single 'R'
Wrong Spelling:  inte-r-ex  Correct Spelling:  inte-rr-ex 
Explore spell check of Interrex to spell without errors.