Definition of theme - Environment

Environment means the surroundings of an object or living thing. It may be a Natural environment, like a forest or a built-up environment, like a city. The conditions of an environment can affect the development of an organism. In an environment, every organism can interact and influence each other, so every little action will in turn cause something to be affected.

Source: http://en.wikipedia.org/wiki/Environment
http://dictionary.reference.com/browse/environment