Does any one know or have a word for two arcs whose measures sum to 360 degrees? I seem to recall having read that they are called complementary arcs. My students have suggested bi-supplementary or circplementary. As I read the etymology, both complementary and supplementary mean virtually the same thing "something that completes or fills up". Thus its use in complementary sets. Likewise looking for a word for for two angles whose sum is 270 degrees? Their contributions have been tricomplementary or sesquisupplementary.