They aren't; their entire shape is a complete circle. From our position during rainbow formation, we can only see half of the rainbow.
The answer would depend on a semicircular WHAT. Semicircular is an adjective, there is no noun to go with it.The answer would depend on a semicircular WHAT. Semicircular is an adjective, there is no noun to go with it.The answer would depend on a semicircular WHAT. Semicircular is an adjective, there is no noun to go with it.The answer would depend on a semicircular WHAT. Semicircular is an adjective, there is no noun to go with it.
Semicircular Canals
The semicircular canals and the vestible are responsible for balance.
Actually it is circular but usually the sun needs to be quite low in the sky for the angle of the sunbeams hitting the raindrops to be suitable to create a rainbow visible from the ground. But, when that happens, a part of the rainbow is cut-off by the horizon and so it appears semicircular. Full circles are rare but have been seen/photographed.
semicircular canals
semicircular ducts
No. Semicircular canals are located in the vestibule of the ear and are membranous that contain receptor cells; semicircular ducts house dynamic equilibrium receptors and contain an enlarged region and a receptor region and that respond to angular motion.
The semicircular ducts are an organ of balance located in the inner ear.
semicircular canals
Apse
perilymph
Endolymph