Atto (symbol a) is a unit prefix in the metric system denoting a factor of 10−18 or 0.000000000000000001.
| SI prefixes [edit] | |
| Negative prefixes | deci • centi • milli • micro • nano • pico • femto • atto • zepto • yocto |
|---|---|
| Positive prefixes | deca • hecto • kilo • mega • giga • tera • peta • exa • zetta • yotta |
| Binary prefixes | kibi • mebi • gibi • tebi • pebi • exbi • zebi • yobi |