Look up kilo in Wiktionary, the free dictionary. 
Kilo is a decimal unit prefix in the metric system denoting multiplication by one thousand (10^{3}). It is used in the International System of Units where it has the unit symbol k, in lower case.
The prefix kilo is derived from the Greek word χίλιοι (chilioi), meaning "thousand". It was originally adopted by Antoine Lavoisier's research group in 1795, and introduced into the metric system in France with its establishment in 1799.
In 19th century English it was sometimes spelled chilio, in line with a puristic opinion by Thomas Young^{[1]}^{[2]}
By extension, currencies are also sometimes preceded by the prefix kilo:
For the kilobyte, a second definition has been in common use in some fields of computer science and information technology. It uses kilobyte to mean 2^{10} bytes (= 1024 bytes), because of the mathematical coincidence that 2^{10} is approximately 10^{3}. The reason for this application is that digital hardware and architectures natively use base 2 exponentiation, and not decimal systems. JEDEC memory standards still permit this definition, but acknowledge the correct SI usage.
NIST comments on the confusion caused by these contrasting definitions: "Faced with this reality, the IEEE Standards Board decided that IEEE standards will use the conventional, internationally adopted, definitions of the SI prefixes", instead of kilo for 1024.^{[3]} To address this conflict, a new set of binary prefixes has been introduced, which is based on powers of 2. Therefore, 1024 bytes are defined as one kibibyte (1 KiB).
When units occur in exponentiation, such as in square and cubic forms, any multiplier prefix is considered part of the unit, and thus included in the exponentiation.
Prefix  Base 1000  Base 10  Decimal  English word  Adoption^{[nb 1]}  

Name  Symbol  Short scale  Long scale  
yotta  Y  1000^{8}  10^{24}  1000000000000000000000000  septillion  quadrillion  1991 
zetta  Z  1000^{7}  10^{21}  1000000000000000000000  sextillion  trilliard  1991 
exa  E  1000^{6}  10^{18}  1000000000000000000  quintillion  trillion  1975 
peta  P  1000^{5}  10^{15}  1000000000000000  quadrillion  billiard  1975 
tera  T  1000^{4}  10^{12}  1000000000000  trillion  billion  1960 
giga  G  1000^{3}  10^{9}  1000000000  billion  milliard  1960 
mega  M  1000^{2}  10^{6}  1000000  million  1873  
kilo  k  1000^{1}  10^{3}  1000  thousand  1795  
hecto  h  1000^{2/3}  10^{2}  100  hundred  1795  
deca  da  1000^{1/3}  10^{1}  10  ten  1795  
1000^{0}  10^{0}  1  one  –  
deci  d  1000^{−1/3}  10^{−1}  0.1  tenth  1795  
centi  c  1000^{−2/3}  10^{−2}  0.01  hundredth  1795  
milli  m  1000^{−1}  10^{−3}  0.001  thousandth  1795  
micro  μ  1000^{−2}  10^{−6}  0.000001  millionth  1873  
nano  n  1000^{−3}  10^{−9}  0.000000001  billionth  milliardth  1960 
pico  p  1000^{−4}  10^{−12}  0.000000000001  trillionth  billionth  1960 
femto  f  1000^{−5}  10^{−15}  0.000000000000001  quadrillionth  billiardth  1964 
atto  a  1000^{−6}  10^{−18}  0.000000000000000001  quintillionth  trillionth  1964 
zepto  z  1000^{−7}  10^{−21}  0.000000000000000000001  sextillionth  trilliardth  1991 
yocto  y  1000^{−8}  10^{−24}  0.000000000000000000000001  septillionth  quadrillionth  1991 
