Ecliptic longitude is a coordinate used in astronomy to specify the position of an object in the sky relative to the ecliptic plane, which is the apparent path of the Sun across the celestial sphere. It is measured in degrees, starting from the point of the vernal equinox, which is defined as 0 degrees. The longitude increases as you move eastward along the ecliptic. This measurement helps astronomers locate celestial bodies, such as planets and stars, in relation to the Earth. Ecliptic longitude is essential for understanding the positions of these objects over time and is a key component in celestial navigation and astrological charts.