Jose Rizal

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Definition of Measurement
Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc., to a unit of measurement, such as the meter, second or degree Celsius. The science of measurement is called metrology. The English word measurement originates from the Latin mēnsūra and the verb metiri through the Middle French mesure. Reference:

Measurement Quantities
*Basic Fundamental
Quantity name/s| (Common) Quantity symbol/s| SI unit name| SI unit symbol| Dimension symbol| Length, width, height, depth| a, b, c, d, h, l, r, s, w, x, y, z| metre| m| [L]| Time| t| second| s| [T]|

Mass| m| kilogram| kg| [M]|
Temperature| T, θ| kelvin| K| [Θ]|
Amount of substance, number of moles| n| mole| mol| [N]| Electric current| i, I| ampere| A| [I]|
Luminous intensity| Iv| candela| Cd| [J]|
Plane angle| α, β, γ, θ, φ, χ| radian| rad| dimensionless| Solid angle| ω, Ω| steradian| sr| dimensionless|

Derived Quantities


(Common) Quantity name/s| (Common) Quantity symbol| SI unit| Dimension| (Spatial) position (vector)| r, R, a, d| m| [L]|
Angular position, angle of rotation (can be treated as vector or scalar)| θ, θ| rad| dimensionless| Area, cross-section| A, S, Ω| m2| [L]2|
Vector area (Magnitude of surface area, directed normal totangential plane of surface)| | m2| [L]2| Volume| τ, V| m3| [L]3|

Quantity| Typical symbols| Definition| Meaning, usage| Dimension| Quantity| q| q| Amount of a property| [q]|
Rate of change of quantity, Time derivative| | | Rate of change of property with respect to time| [q] [T]−1| Quantity spatial density| ρ = volume density (n = 3), σ = surface density (n = 2), λ = linear density (n = 1)No common symbol for n-space density, here ρn is used.| | Amount of property per unit n-space(length, area, volume or higher dimensions)| [q][L]-n| Specific quantity| qm| | Amount of property per unit mass| [q][L]-n| Molar quantity| qn| | Amount of property per mole of substance| [q][L]-n| Quantity gradient (if q is a scalar field.| | | Rate of change of property with respect to position| [q] [L]−1| Spectral quantity (for EM waves)| qv, qν, qλ| Two definitions are used, for frequency and wavelength:

| Amount of property per unit wavelength or frequency.| [q][L]−1 (qλ)[q][T] (qν)| Flux, flow (synonymous)| ΦF, F| Two definitions are used;Transport mechanics, nuclear physics/particle physics: Vector field:

| Flow of a property though a cross-section/surface boundary.| [q] [T]−1 [L]−2, [F] [L]2| Flux density| F| | Flow of a property though a cross-section/surface boundary per unit cross-section/surface area| [F]| Current| i, I| | Rate of flow of property through a crosssection/ surface boundary| [q] [T]−1| Current density (sometimes called flux density in transport mechanics)| j, J| | Rate of flow of property per unit cross-section/surface area| [q] [T]−1 [L]−2|


System of Units

Unit name| Unit
symbol| Quantity| Definition (Incomplete)| Dimension
metre| m| length| * Original (1793): 1⁄10000000 of the meridian through Paris between the North Pole and the EquatorFG * Current (1983): The distance travelled by light in vacuum in 1⁄299792458 of a second| L| kilogram[note 1]| kg| mass| * Original (1793): The grave was defined as being the weight [mass] of one cubic decimetre of pure water at its freezing point.FG * Current (1889): The mass of the International Prototype Kilogram| M| second| s| time| * Original (Medieval): 1⁄86400 of a day * Current (1967): The duration of 9 192 631 770 periods of the radiation corresponding to...
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