trilione

Trilione is a numeric term used in the long-scale numbering system, denoting 10^18 (a one followed by eighteen zeros). The word is primarily found in Italian, where trilione is the standard name for this quantity. In the long scale, each new term is a million times larger than the previous one, so trilione follows bilione (10^12). The corresponding name in the English short scale for 10^18 is quintillion. Because of differences between number naming systems, trilione can be a source of confusion in translations between Italian and English.

The term's derivation reflects the Italian tradition of forming large-number names from milione and prefixes: tri- meaning three and -lione from milione. In modern Italian mathematical usage, long-scale terms are still recognized, but the short-scale system is also widely understood due to international financial communication; many Italian speakers may default to short-scale equivalents in international contexts.

In practice, trilione is used when discussing very large quantities, such as national debts, populations, or scientific measurements at astronomical scales, but in everyday use such enormous figures are rare. When converting between scales, 1 trilione (long scale) equals 1 quintillion (short scale).