illion

Illion is a productive suffix used in the names of very large numbers in English, forming a family of terms such as million, billion, trillion, quadrillion, and so on. It is not a number by itself but a linguistic pattern that denotes increasing orders of magnitude when combined with numerical prefixes.

Etymology and formation of illion names trace back to the word million, which itself comes from Old French and Italian forms of the Latin mille, meaning thousand. The -illion suffix was extended to name larger scales, producing a systematic series in which a prefix attached to -illion indicates a higher order of magnitude. The exact historical development is complex, but today -illion serves as a conventional basis for naming large powers of ten.

Usage and scale differ between the short scale and the long scale. In the short scale, used in most modern English-speaking countries, the sequence is: million (10^6), billion (10^9), trillion (10^12), quadrillion (10^15), quintillion (10^18), sextillion (10^21), septillion (10^24), octillion (10^27), nonillion (10^30), decillion (10^33), and so forth. In the long scale, historically used in parts of Europe, billion means 10^12, trillion 10^18, quadrillion 10^24, and so on, with each step representing a different power of one million. These differences can affect cross-border references to large numbers.

In practice, illion names are often used in mathematical or theoretical discussions, science fiction, or to convey very large quantities. For precise measurements, it is important to specify the scale being used.