\begin{definition}[Definition:Astronomical Distance Units/Astronomical Unit]
The '''astronomical unit''' is a derived unit of length.
It is defined as being $149 \, 597 \, 870 \, 700$ metres.
The '''astronomical unit''' is the standard unit of measurement used by astronomers when discussing distances within the solar system.
It is derived as the approximate mean distance from the Earth to the Sun.
\end{definition}