What measurement does ppm stand for?

PPM stands for "Parts per Million," which is a unit of measurement used to express very dilute concentrations of substances. It denotes the number of parts of a substance found in one million parts of a solution or mixture. This measurement is crucial in various fields such as chemistry, environmental science, and health, particularly when assessing pollutant levels or contaminants in water, soil, and air.

Understanding the concept of PPM is essential because it helps in quantifying and communicating the presence of substances at low concentrations, ensuring compliance with safety and health regulations. The other options do not accurately define the common use of the term—parts per minute measures frequency or rate, percentage per million is not a standard term, and parts per meter does not relate to concentration.