valley

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. An elongated lowland between ranges of mountains, hills, or other uplands, often having a river or stream running along the bottom.
2. n. An extensive area of land drained or irrigated by a river system.
3. n. A depression or hollow resembling or suggesting a valley, as the point at which the two slopes of a roof meet.

Century Dictionary and Cyclopedia

1. n. The depression between two ridges of a tooth, typically shown in such molars as those of the tapir and mastodon: correlated with lake, which is a depression surrounded by a raised ridge of enamel such as occurs in the molars of a horse.
2. n. A depression, or a relatively low and somewhat level area, more or less completely inclosed by hills or mountains; the basin of a stream of any size, or the area drained by it, and, in accordance with more general usage, the part of that area which lies near the stream and is not much raised above its level. The surface of a mountainous region is made up of hills (or mountains) and valleys; but over those great expanses of country where uniformity of level is the dominant feature the term valley gives way to some other designation more specific in its character: thus, in English, heath, prairie, savanna, plain, desert; in Spanish-speaking countries, campo, pampa, llano, páramo; in the Russian empire, steppe, tundra; in South Africa, veldt, etc. All the tracts thus designated lie within the basins of certain rivers, and thus technically form parts of the valleys of those rivers, but convenience demands and justifies the special designation. So, on the other hand, in mountainous countries, or even in those in which the surface is only moderately broken, the valleys have their forms characterized by terms suited to express the great variety of features which they exhibit: thus, in English, dale, dell, dingle, cove, comb, gully, ravine, gorge, defile, chasm, and many others; in French, combe, cluse, cirque, etc.; in Spanish, cañada (changed to cañon in the western United States), barranca, quebrada, etc.; and so through all the various languages and countries. The forms of valleys are so numerous, and their existence dependent on such complicated and varied conditions, that a satisfactory classification of them is not possible. The simplest division of them, from the orographic point of view, is into longitudinal and transverse: the former are parallel with the mountain-ranges to which they belong; the latter, more or less nearly at right angles to them. Of longitudinal valleys the “Great Valley” of the Appalachian range offers an excellent example, this being parallel with the Blue Ridge, and having a development of about 500 miles in length in Pennsylvania and Virginia, and a very uniform width within those States of rarely less than 12 or more than 20 miles. The valleys of the Rhone and the Rhine in their upper portions—which rivers start from near the same point, and flow in exactly opposite directions, parallel with the crest of the Alps—furnish another good illustration of a longitudinal valley; while an equally satisfactory example of a transverse one is seen in the course of the Rhone from Martigny to the Lake of Geneva, where that river follows a direction at right angles to that which it has in the upper part of its course. Longitudinal valleys are more distinctly orographic in character than are the transverse—that is, their origin is due primarily to the same causes which have governed the position and direction of the ranges which make up the mountain-system to which they belong. Transverse valleys, on the other hand, though not necessarily independent of preexisting breaks and faults, are, in general, chiefly the result of erosive agencies—by which, indeed, the forms of almost all valleys have been more or less profoundly modified. In some chains, however, notably in the Himalayas, the tendency of large streams flowing in longitudinal valleys to break transversely through lofty and precipitous ranges, and pass out of what seems their natural and predestined course, is an extraordinary orographic feature, and one which has not received a satisfactory explanation.
3. n. Hence, any similar depression of any size.
4. n. Specifically, in architecture, the internal angle formed by the meeting of two inclined sides of a roof. The rafter which supports the valley is called the valley-rafter or valley-piece, and the board fixed upon it for the metallic gutter to lie upon is termed the valleyboard.

Wiktionary

1. n. An elongated depression between hills or mountains, often with a river flowing through it.
2. n. The area which drains into a river.
3. n. Any structure resembling one, e.g, the meeting point of two pitched roofs.
4. n. The internal angle formed by the intersection of two sloping roof planes.

GNU Webster's 1913

1. n. The space inclosed between ranges of hills or mountains; the strip of land at the bottom of the depressions intersecting a country, including usually the bed of a stream, with frequently broad alluvial plains on one or both sides of the stream. Also used figuratively.
2. n. The place of meeting of two slopes of a roof, which have their plates running in different directions, and form on the plan a reëntrant angle.
3. n. The depression formed by the meeting of two slopes on a flat roof.

WordNet 3.0

1. n. a long depression in the surface of the land that usually contains a river