1. The circumstances or conditions that surround one; surroundings.
2. The totality of circumstances surrounding an organism or group of organisms, especially:
   1. The combination of external physical conditions that affect and influence the growth, development, and survival of organisms: "We shall never understand the natural environment until we see it as a living organism" (Paul Brooks).
   2. The complex of social and cultural conditions affecting the nature of an individual or community.
3. Computer Science.
   1. The entire set of conditions under which one operates a computer, as it relates to the hardware, operating platform, or operating system.
   2. An area of a computer's memory used by the operating system and some programs to store certain variables to which they need frequent access.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.