angstrom

Name	Symbol	Quantity	SI units
angstrom, ångström	Å	length	10⁻¹⁰  m
The angstrom, or ångström, symbol Å, is a non-SI unit of length. The angstrom is not accepted for use with the SI. One angstrom is equal to 10^-10 m or 0.1 nanometre.
Definition			c Δν_Cs^-1
$1 \mspace{4mu} \text{A} \mspace{6mu} = \dfrac{9 \mspace{4mu} 192 \mspace{4mu} 631 \mspace{4mu} 770}{(10^{10})(299 \mspace{4mu} 792 \mspace{4mu} 458)} \mspace{6mu} \dfrac{c}{\Delta \nu _{Cs}}\\ \\ \\ 1 \mspace{4mu} \text{A} \mspace{6mu} \approx 3.066 \mspace{4mu} \mspace{4mu} 331 \mspace{4mu} 898 \mspace{4mu} 849 \mspace{4mu} 836 \mspace{4mu} 976 \times10^{-9} \mspace{6mu} c \mspace{4mu} {\Delta \nu _{Cs}}^{-1}$

The unit is named after the Swedish physicist Anders Jonas Ångström (1814 – 1874).