xenna-

From Ancient Greek ἐννέα (ennéa, “nine”), for the ninth order of 10³, and the letter x, as the third term in a series running backwards through the alphabet (after zetta- and yotta-). The final a conforms to the final vowel of the SI series from mega- upwards.

• IPA^(key): /ˈzɛnə/

xenna-

1. (neologism) In metric systems of units, multiplying the unit to which it is attached by 10²⁷; octillion-. Symbol: X
   • 1994, IPC Magazines, New Scientist Vol. 144, page 81:

     The SI prefixes above are not the only extreme ones. Others such as xenno (x) (10^-27) and xenna (X) (10²⁷), or vendeko (v) (10^-33) and vendeka (V) (10³³) exist, and can help simplify the expression of extreme numbers.

   • 1997, Council of Scientific & Industrial Research, Science Reporter Vol. 34, page 23:

     If we try to calculate the mass of earth it comes to 6 xennagrams which is nothing but 6x10²⁴ kilograms or 6x10²⁷ gms.

   • 2015, Claude Phipps, No Wonder You Wonder!: Great Inventions and Scientific Mysteries, Springer, page 62:

     But that's nothing: our universe is about 0.8 Xm (Xennametres, billions of billions of billions of metres) in diameter.

   • For more examples of usage of this term, see Citations:xenna-.

• hella-

• xenno-

Not a standard prefix in the metric International System of Units.

• annex