Nano (symbol n) is a unit prefix meaning one billionth. Used primarily with the metric system, this prefix denotes a factor of 10^{−9} or 0.000000001. It is frequently encountered in science and electronics for prefixing units of time and length.
The prefix derives from the Greek νᾶνος (Latin nanus), meaning "dwarf". The General Conference on Weights and Measures (CGPM) officially endorsed the usage of nano as a standard prefix in 1960.
When used as a prefix for something other than a unit of measure (as for example in words like "nanoscience"), nano refers to nanotechnology, or means "on a scale of nanometres" (nanoscale).
Prefix  Base 10  Decimal  Adoption ^{[nb 1]}  

Name  Symbol  
quetta  Q  10^{30}  1000000000000000000000000000000  2022^{[2]} 
ronna  R  10^{27}  1000000000000000000000000000  
yotta  Y  10^{24}  1000000000000000000000000  1991 
zetta  Z  10^{21}  1000000000000000000000  
exa  E  10^{18}  1000000000000000000  1975^{[3]} 
peta  P  10^{15}  1000000000000000  
tera  T  10^{12}  1000000000000  1960 
giga  G  10^{9}  1000000000  
mega  M  10^{6}  1000000  1873 
kilo  k  10^{3}  1000  1795 
hecto  h  10^{2}  100  
deca  da  10^{1}  10  
—  —  10^{0}  1  — 
deci  d  10^{−1}  0.1  1795 
centi  c  10^{−2}  0.01  
milli  m  10^{−3}  0.001  
micro  μ  10^{−6}  0.000001  1873 
nano  n  10^{−9}  0.000000001  1960 
pico  p  10^{−12}  0.000000000001  
femto  f  10^{−15}  0.000000000000001  1964 
atto  a  10^{−18}  0.000000000000000001  
zepto  z  10^{−21}  0.000000000000000000001  1991 
yocto  y  10^{−24}  0.000000000000000000000001  
ronto  r  10^{−27}  0.000000000000000000000000001  2022^{[2]} 
quecto  q  10^{−30}  0.000000000000000000000000000001  

The nanometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: nm), or nanometer (American spelling), is a unit of length in the International System of Units (SI), equal to one billionth (short scale) of a meter (0.000000001 m) and to 1000 picometres. One nanometre can be expressed in scientific notation as 1 × 10^{9} m and as 1/1000000000 m.
Xrays have a wavelength ranging from the size of 0.01 nm to 10 nm.
Human fingernails grow at approximately one nanometer per second.^{[4]}
A nanosecond (ns) is a unit of time in the International System of Units (SI) equal to one billionth of a second, that is, 1⁄1 000 000 000 of a second, or 10^{−9} seconds.
The term combines the SI prefix nano indicating a 1 billionth submultiple of an SI unit (e.g. nanogram, nanometre, etc.) and second, the primary unit of time in the SI.
A nanosecond is to one second, as one second is to approximately 31.69 years.
A nanosecond is equal to 1000 picoseconds or 1⁄1000 microsecond. Time units ranging between 10^{−8} and 10^{−7} seconds are typically expressed as tens or hundreds of nanoseconds.
Time units of this granularity are commonly found in telecommunications, pulsed lasers, and related aspects of electronics.