The amount of a given substance in a stated unit of measure. Common methods of stating concentration are percent by weight or by volume, weight per unit volume, normality, etc
US Department of Labor, Glossary of Terms - Occupational Safety & Health Administration, OSHA Office of Training and Education, Construction Safety and Health Outreach Program, Washington, D.C., USA 1996. https://www.osha.gov/doc/outreachtraining/htmlfile s/hazglos.html, (OSHA/ Const - Amer) {614}