The conversion of atmospheric nitrogen into compounds, such as ammonia, by natural agencies or various industrial processes.
The conversion by certain soil microorganisms, such as rhizobia, of atmospheric nitrogen into compounds that plants and other organisms can assimilate.
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.