Source:http://linkedlifedata.com/resource/umls/id/C0017110
MSH: The vapor state of matter; nonelastic fluids in which the molecules are in free movement and their mean positions far apart. Gases tend to expand indefinitely, to diffuse and mix readily with other gases, to have definite relations of volume, temperature, and pressure, and to condense or liquefy at low temperatures or under sufficient pressure. (Grant & Hackh's Chemical Dictionary, 5th ed),CSP: vapor state of matter; nonelastic fluids in which the molecules are in free movement and their mean positions far apart.,NCI: A fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely.