SI units

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SI units (Système international d'unités) are now the general fundamental units for scientific work. They are based on seven base units for seven base quantities which we assume to be mutually independent. The main basic units with which you will be concerned are the metre (m), the kilogram (kg) and the second (s). Other non-SI units, notably minute (min), hour (h), degree Celsius (°C) and litre (l) are still commonly used in science.

The Seven Base Units are as Follows:

Base Quantity Name Symbol
Length metre m
Time second s
Mass kilogram kg
Amount of Substance mole mol
Thermodynamic Temperature kelvin K
Electric Current ampere A
Luminous Intensity candela cd

When using abbreviations, never add the letter "s" in an attempt to signify plurals. Below are some of the common symbols:

Symbol Prefix Factor
c centi 10-2
m milli 10-3
μ micro 10-6
n nano 10-9
p pico 10-12

(1 l = 103 ml = 106 μl, 1g = 103 mg = 106 μg)

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