When people talk about the environment, they often mean the parts of the world that are still partly wild. Sometimes this is called the natural environment. The cities where people mostly live is sometimes called the built environment.

The environment can be the air, the oceans, the soil, the plants or the animals. Usually it is all of them.

Together, all living things in the wild make up a pattern where living things, on balance, all survive, even though some are food for others. However, people can upset this balance, in part because there are now so many of us, and in part because we can use large machines to change everything quickly.