Definition

Parts per million (ppm) is a unit of measurement used to express the concentration of a substance in a mixture, typically in gases or liquids. It signifies the ratio of the quantity of a particular substance to the total quantity of the mixture, with the substance being present at one part per million.

Mathematically, ppm is defined as:

1 ppm = 1 \1,000,000 parts

In other words, 1 ppm represents one part of the substance in every million parts of the mixture. This unit is commonly used in various fields, including chemistry, environmental science, and industry, to specify relatively low concentrations of substances. It is particularly useful for quantifying substances that are present in small amounts, but not at trace levels.