I remember my geography classes in middle and high school explaining the difference between the earth’s latitudes and longitudes. I was taught latitudes go East – West and are parallel to each other away from the equator. Longitudes go North – South and are also parallel to each other.
I remember being taught that the circumference of the earth is usually the distance around the earth at the equator – the zero (0) degree latitude. Scientists now measure it as being 24,901 miles in length.
You can technically say, however that every longitudinal distance around the earth (going through the North and South Poles) is also a circumference, but, they may be all different lengths than at the equator because the earth has been discovered to be pear-shaped.