Millenium = 1000 years Meganum/menialmore = 1 million years Giganum/eon = 1 billion years Terranum = 1 Trillion years Pettanum = 1 Quadrillion years Exannum/Exannus = 1 Quintillion years Zettanum = 1 Sixtillion years Yottanum = 1 Septillion years Xonnanum/Bettanum = 1 Octillion years Alphanum = 1 Nonillion years Decanum = 1 Decillion years Megadecanum/Undecanum=1 undecillion years Gigadecanum/Duodecanum=1 duodecillion years