To hear audio pronunciation of this topic, purchase a subscription or log in.

1. In geography, an open expanse of land.
2. In the arts and sciences, a discipline or an area of study.
3. In physics, a region of space in which a given force operates or a given condition exists.
4. In experimental situations, a place of natural conditions, as opposed to a controlled environment, such as a laboratory or a hospital.

There's more to see -- the rest of this topic is available only to subscribers.