Latitude
From GeoWiki
Latitude, represented by a series of horizontal lines on a map - or horizontal rings on a globe - is the angular distance of a point on the Earth either north or south of the Equator. There are 180 degrees of latitude, 90 north and 90 south of the equator, which is defined as 0°. Lines of latitude are ofter refered to as "parallels". N90° and S90° coincide with the north and south poles, respectively.
Only the equitorial line of latitude forms a Great Circle - compare this to longitude where every line of longitude is a Great Circle.