Meridians, as lines of longitude, are measured in degrees. The Prime Meridian, as the starting point, is 0 (zero) degrees. Lines west of the Prime Meridian are either called "west", as in "the longitude of Los Angeles, California is 118 degrees west", or as a negative number: "the longitude of Los Angeles, California is -118 degrees". Going the other direction, east of the Prime Meridian is always said as a positive number: "The longitude of Mecca is about 40 degrees east," or just "The longitude of Mecca is about 40 degrees."