Great circle and Line of longitude

Great circle noun - A circular line on the surface of a sphere formed by intersecting it with a plane passing through the center.

Line of longitude and great circle are semantically related. In some cases you can replace phrase "Line of longitude" with "Great circle", this phrases are similar.

Line of longitude noun - An imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator.

Great circle and line of longitude are semantically related. You can use "Great circle" instead a noun phrase "Line of longitude".