In geometry, length refers to the longest dimension of a two- or three-dimensional object. The other dimensions are height and width. Length may also refer to the duration of an event or passage of time. In some instances, length is used to compare the size of two or more objects.
Cuts of lumber are labeled according to their thickness and width, but priced according to length. For example, the term "2x4" refers to a milled board that is approximately 1.5 inches thick and 3.5 inches wide. It is commonly used for studs and framing, but a builder might order a variety of lengths, such as 8-foot, 10-foot or 12-foot boards. Another example of length as a term for a physical dimension is a professional football field, which is 100 yards in length from end zone to end zone.
When used to describe the duration of an event or the passage of time, length is measured in units of time. A car trip from New York to Los Angeles might be several days in length. The average movie is approximately two hours in length.
Length may also be used to describe a hard-to-measure or inexact distance, such as an arm's length, great lengths or a length of rope. In these cases, the context determines how length should be interpreted.