miljarddels

Miljarddels is a fractional unit used in Scandinavian languages to denote one part in a milliard, i.e., one part in a billion. It equals 1/1,000,000,000, which is 10 to the power of −9. In Swedish, Norwegian and Danish, miljard means a thousand million, so a miljarddel represents that same 10^−9 fraction of a given quantity.

Usage and context can vary by field, but miljarddel is commonly employed to express very small quantities in science, statistics or economics. When quantities are described in terms of extremely small concentrations or probabilities, miljarddel (often conceptually aligned with parts per billion) conveys the idea of one unit in a billion units.

Notation and numerical form: one miljarddel is the decimal 0.000000001. As a percentage, it is 0.0000001%. In many contexts, especially in English texts, parts per billion (ppb) is used to express the same scale, with one ppb equal to one miljarddel of the total amount.

Notes: The term reflects the Scandinavian naming of numbers, where miljard denotes 10^9. It is distinct from millionth (miljonedal) and from SI prefixes like nano, though 10^−9 corresponds to the nano scale in SI. The term is primarily used in technical writing and statistical reporting, and may be unfamiliar outside regions that use the term miljarddel.

See also: parts per billion, ppb, decimal fractions.