Definition:Linear Measure
Definition
Linear measure is the means of measurement of the magnitude of a physical displacement.
As such, linear measure is a scalar quantity.
Symbol
The usual symbol used to denote linear measure is $l$.
Dimension
Linear measure is one of the fundamental dimensions of physics.
In dimensional analysis it is assigned the symbol $\mathsf L$.
Units
The SI unit of linear measure is the metre.
The CGS unit of linear measure is the centimetre.
The FPS unit of linear measure is the foot.
Length
Length is linear measure taken in a particular direction.
Usually, in multi-dimensional figures, the dimension in which the linear measure is greatest is referred to as length.
It is the most widely used term for linear measure, as it is the standard term used when only one dimension is under consideration.
Length is the fundamental notion of Euclidean geometry, never defined but regarded as an intuitive concept at the basis of every geometrical theorem.
Breadth
Breadth is linear measure in a dimension perpendicular to length.
In the context of a two-dimensional geometric figure, the breadth is in the plane of that figure.
In a three-dimensional figure, the choice of which direction is referred to as breadth is often arbitrary.
Depth
Depth is linear measure in a dimension perpendicular to both length and breadth.
The choice of depth is often arbitrary, although in two-dimensional diagrams of three-dimensional figures, depth is usually imagined as being the dimension perpendicular to the plane the figure is drawn in.
It is typically used to measure the distance downwards from the surface of a body of liquid.
Height
Height, like depth, is used as a term for linear measure in a dimension perpendicular to both length and breadth.
However, whereas depth has connotations of down, height is used for distances up from the plane.
Thickness
Thickness, like breadth, is used as a term for linear measure in a dimension perpendicular to both length and depth.
However, whereas breadth has connotations of across, thickness is used for distances through the solid figure.
Distance
The distance between two points $A$ and $B$ in space is defined as the length of a straight line segment that would be drawn from $A$ to $B$.
Also see
Sources
- 1969: J.C. Anderson, D.M. Hum, B.G. Neal and J.H. Whitelaw: Data and Formulae for Engineering Students (2nd ed.) ... (previous) ... (next): $1.$ Units and Abbreviations: $1.2$ SI units $(1)$ Basic units
- 1976: Ralph J. Smith: Circuits, Devices and Systems (3rd ed.) ... (previous) ... (next): Chapter $1$: Electrical Quantities: Definitions and Laws: The International System of Units: Table $1$-$1$ Basic Quantities
- 1998: David Nelson: The Penguin Dictionary of Mathematics (2nd ed.) ... (previous) ... (next): scalar quantity
- 2008: David Nelson: The Penguin Dictionary of Mathematics (4th ed.) ... (previous) ... (next): scalar quantity