The angular distance measured along the earth's equator between the meridian passing through the point and the Greenwich Meridian or zero meridian: In her astronomy class, Alice learned that a longitude was any imaginary line at right angles to the equator of the planet Earth and which went through the North and South Poles.

Longitude measured (in degrees) along the ecliptic to the east from the vernal equinox: The Symbol for the celestial longitude is the Greek letter λ or lambda.

The angular distance between a celestial body and the first point of Aries, measured along the ecliptic.