Geometric terms of location

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Geometric terms of location describe directions or positions relative to the shape of an object. These terms are used in descriptions of engineering, physics, and other sciences, as well as ordinary day to day discourse.

Though these terms by themselves may be somewhat ambiguous, they are usually used in a context in which their meaning is clear. For example, when referring to a drive shaft it is clear what is meant by axial or radial directions. Or, in a free body diagram, one may similarly infer a sense of orientation by the forces or other vectors represented.


Common geometric terms of location are:

  • Adjacent – next to
  • Axial – along the center of a round body, or the axis of rotation of a body
  • Azimuthal or circumferential – following around a curve or circumference of an object. For instance, the pattern of cells in Taylor–Couette flow varies along the azimuth of the experiment.
  • Collinear – in the same line
  • Degree of freedom – axis direction, see six degrees of freedom
  • Elevation – along a curve from a point on the horizon to the zenith, directly overhead.
  • Depression – along a curve from a point on the horizon to the nadir, directly below.
  • Lateral – spanning the width of a body. The distinction between width and length may be unclear out of context.
  • Lineal – following along a given path. The shape of the path is not necessarily straight (compare to linear). For instance, a length of rope might be measured in lineal meters or feet. See arc length.
  • Longitudinal – spanning the length of a body.
  • Orthogonal – at a right angle (at the point of intersection).
  • Parallel – in the same direction.
  • Perpendicular – at right angles to, synonym to orthogonal.
  • Radial – along a direction pointing along a radius from the center of an object, or perpendicular to a curved path.
  • Tangential – intersecting a curve at a point and parallel to the curve at that point.
  • Transverse – intersecting at any angle, i.e. not parallel.
  • Vertical – spanning the height of a body.

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