1: a branch of science concerned with the interrelationship of organisms and their environments
2: the totality or pattern of relations between organisms and their environment
1: a branch of sociology dealing especially with the spatial and temporal interrelationships between humans and their economic, social, and political organization
2: the ecology of human communities and populations especially as concerned with preservation of environmental quality (as of air or water) through proper application of conservation and civil engineering practices
Source: Miriam Webster (m-w.com)
The word “ecology” is often used more loosely in such terms as social ecology and deep ecology and in common parlance as a synonym for the natural environment or environmentalism. Likewise “ecologic” or “ecological” is often taken in the sense of environmentally friendly.