Parallels of latitude are imaginary circles drawn round the Earth parallel to the equator. The parallels are numbered according to the angle formed between a line from the line of latitude to the centre of the Earth and a line from the centre of the Earth to the equator. Those regions lying within the Arctic and Antarctic circles, having values of 66.5° to 90°, are termed high latitudes. Low latitudes lie between 23.5° north and south of the equator, i.e. within the tropics. Mid-latitudes, also known as temperate latitudes, lie between the two.