The length is one of the fundamental physical magnitudes, while it can not be defined in terms of other magnitudes that can be measured. In many systems of measurement, the length is a fundamental unit, from which other derive.
Length is a measure of a dimension (linear, for example m), while the area is a measure of two dimensions (square, for example m²), and the volume is a measure of three dimensions (cubic eg m³ ).
However, according to the special theory of relativity (Albert Einstein, 1905), the length is not an intrinsic property of any object as two observers could measure the same object and get different results (Lorentz contraction).
The long dimension or length of an object is three-dimensional measurement of axis Y. This is the traditional way in which appointed the longest part of an object (in terms of horizontal base and its vertical high).
In two-dimensional Cartesian coordinates, where only the XY axes is called "long". X values indicate the width (horizontal axis), and and height (vertical axis).
In mathematics, the distance between two points in Euclidean space is the length of the line segment joining them expressed numerically. In more complex spaces, as defined in non-Euclidean geometry, the "shortest path" between two points is a curve segment.
In physical distance is a scalar quantity, which is expressed in units of length.