astronomical unit: a unit of length used for distances within the solar system; equal to the mean distance between the Earth and the Sun (approximately 93 million miles or 150 million kilometers)
linear unit: a unit of measurement of length
ijtihad: the endeavor of a Moslem scholar to derive a rule of divine law from the Koran and Hadith without relying on the views of other scholars; by the end of the 10th century theologians decided that debate on such matters would be closed and Muslim theology and law were frozen