* Canyon: Typically refers to a deep, narrow valley with steep, often vertical sides, carved out by a river or stream over a long period of time. The Grand Canyon is a famous example.
* Gorge: Similar to a canyon, but often smaller and less dramatic in scale. Gorges are often formed by rivers eroding through resistant rock.
Sometimes, "ravine" can also be used to describe a narrow valley with steep sides, but it's typically smaller than a canyon or gorge.
