- enn-Used for the digit nine to form systematic element names of elements whose existence has been predicted, and which have not yet been given a trivial name.
- ennea-Nine.
- enneaticalOccurring once in every nine times, days, years, etc.; every ninth.
- xenna-Synonym of ronna- (used before an official prefix existed). Symbol: X
- xenno-Synonym of ronto- (used before an official prefix existed). Symbol: x