Particulate matter refers to small particles found in the air that can cause health issues when breathed in. There are several different synonyms for particulate matter, including fine particles, airborne particles, particulate pollution, atmospheric particulate matter, and PM2.5 (referring to particles less than 2.5 micrometers in size). Other related terms include PM10 (particles less than 10 micrometers in size), dust, soot, and smoke. Understanding the different terms for particulate matter is important in recognizing the health risks and environmental impacts associated with air pollution. Governments and organizations around the world use these terms to monitor and regulate air quality and reduce the negative impacts of pollutants on human health and the environment.