the branch of biology concerned with the relations between organisms and their environment
"The study of ecology examines how plants and animals interact within their natural habitats."
The branch of biology dealing with the relationships of organisms with their environment and with each other.
"The study of ecology explores how animals interact with their physical surroundings and compete or cooperate within their ecosystems."
In plain English: Ecology is the study of how living things interact with each other and their environment.
"The local ecology supports many species of birds and insects in this forest reserve."
Usage: Use ecology to refer specifically to scientific study, whereas ecosystem describes an actual community of living things interacting with their physical surroundings. Do not confuse it with economy when discussing financial systems or environmental impact alone without a biological focus.
The word ecology is a direct borrowing from the German term coined in 1866 by Ernst Haeckel. It combines Ancient Greek roots meaning "house" and "the study of," referring to the investigation of living things within their natural environments.