Question

Except for the equator the parallels of latitude are not great circles why

Answer 1

Because other parallels of latitude do not lie on the plane passing through the center of Earth nor do they divide the earth into two equal halves,which only Equator does.Thus Equator is the only latitude which is a Great Circle.

Answer 2

As other parallels of latitude do not lie on the plane passing theough the centre of the Earth.