parts per billion

Definitions

General Science

  • noun a measure of the concentration of a substance in a gas, liquid or solid.

Electronics

  • A unit of proportion, equal to a given amount of anything per billion of the same thing or something else. Used, for instance, as a measure of concentration or to quantify error. For example, five erroneous bits per billion transmitted bits. Its abbreviation is ppb.
http://www.dictionarycentral.com/definition/parts-per-billion.html