This is the 2010 version of this glossary. The definitions in this glossary were initially generated by the students in a senior-level class studying air quality and atmospheric chemistry at Sam Houston State University during the spring of 1995 in a course entitled Environmental Science 440/Chemistry 442, AIR QUALITY. In the main, they wrote these definitions as part of a class requirement. They are updated almost every year. The references found at the end of most entries are an effort to supply additional resources for each of the terms. No supposition of comprehensiveness or absolute correctness can be assumed in any way. Many of the glossary entries have hypertext links to other sites on the Internet. These external links were valid in the spring of 2010.