The source chart from which derived houses or progressions are obtained. In charts that use ‘turned houses’ (as in horary), references to the ‘radical house’ relate to the normal flow of houses, which ties the 1st house to the ascendant. So the radical 10th house is the normal 10th house of the horary, which falls on the midheaven, although this might be used as the ‘turned 4th house’ for a partner. The term derives from the Latin radix, meaning ‘root’. In traditional texts dealing with natal astrology, the birth chart is also frequently referred to as the ‘radix chart’.