Basic Units and Prefixes for Competitive Exams

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Units of measurement

Base units

The International System of Units (System International d ‘Unites’) is founded on seven base quantities, which are assumed to be mutually independent. These base units are:

The International System of Units
The International System of Units

Base quantity

SI hast unit

Symbol for unit

Length

Metre

Mass

Kilogram

Time

Second

Electric Current

Ampere

Temperature

Kelvin

Amount of substance

Mole

Luminous intensity

Candela

Prefixes

Prefixes are used to form decimal multiples and submultiples of Si units. The common prefixes are:

Prefixes Are Used to Form Decimal Multiples and Submultiples of Si Units
Prefixes are used to form decimal multiples and submultiples of Si units

Factor

Prefix

Symbol

tera

T

giga

G

mega

M

kilo

k

hecto

h

deka

da

pico

p

nano

n

micro

μ

milli

m

centi

c

deci

d

The symbol for a prefix is combined with the unit symbol to which it is attached to form a new unit symbol, e.g. kilometer (km), milligram (mg), microsecond (μs).