I get a monthly email newsletter from the American Hiking Society and found this interesting tidbit:
Hiking 101: Geographic terms
A quick glance at any map will tell you there is an abundance of terms for the various geographic forms you will encounter outdoors. After a while the definition of these terms can become confusing and a hiker doesn't always know what to expect out on the trail.
Mountains are mountains, but you will also have to hike uphill on a knob, a hill, a bald (which usually has no trees), or a butte. Bald and butte are largely regional words, indicating that geographic terms can differ from one side of the country to the other.
You'll find water at a river, obviously, but also at a brook, stream, run, creek, branch, and ford. Typically, rivers are thought to be larger than streams and brooks. However, the amount of water you find can depend on the season and whether or not the area has been affected by a drought.
Gaps, gorges, hollows, and valleys generally refer to low areas in a region, while crests and ridges are the highest points. Neither necessarily means you'll be traveling downhill or uphill, just that you've reached the top or bottom of a specific location. You could even be hiking on mostly flat ground.
A pass is simply a low area in a series of mountains or along a ridge that allows one to travel between valleys or low-lying areas without ascending and descending the mountain. Also known as a "notch."
(Source: American Hiking Society's Paperless Trail, September 2012)