Geometric measurement

thumb|upright=1.2|From left to right: a square (geometry)|square, a [[cube and a tesseract. The square is two-dimensional (2D) and bounded by one-dimensional line segments; the cube is three-dimensional (3D) and bounded by two-dimensional squares; the tesseract is four-dimensional (4D) and bounded by three-dimensional cubes. ]] [[File:Dimension levels.svg|thumb|upright=1.2| The first four spatial dimensions, represented in a two-dimensional picture.

vector that is the shortest distance from the initial to the final position of a point P

[[File:Circle-withsegments.svg|thumb|

the distance from the center of the arc to the center of its base

thumb|300px|right|Illustration of the ancient Egyptian measure of Seked compared with the slope of the Great Pyramid of Giza|Great Pyramid

standardized codes for engineers to specify parts for manufacturing

thumb|300px|Schematic representation of difference in grain shape. Two parameters are shown: sphericity (vertical) and Roundness (geology)|rounding (horizontal).

Roundness is the measure of how closely the shape of an object approaches that of a mathematically perfect circle. Roundness applies in two dimensions, such as the cross sectional circles along a cylindrical object such as a shaft or a cylindrical roller for a bearing. In geometric dimensioning and tolerancing, control of a cylinder can also include its fidelity to the longitudinal axis, yielding cylindricity. The analogue of roundness in three dimensions (that is, for spheres) is sphericity.