The term 'Astronomical Unit of Distance' is often abbreviated as AU and is a unit of length used to measure distances within the Solar System. It is equal to the average distance between the Earth and the Sun, which is approximately 93 million miles or 150 million kilometers. The term 'Parsec' (6 letters) is also a unit of length used to measure distances in space. It is equal to 3.26 light-years, or about 30.9 trillion kilometers.