demicircle
/ˌdɛmɪˈsɜːrkəl, ˌdɛmɪˈsɪərəl/Definitions
1. noun
A circle or circular area, especially in the shape of half a circle, often used as a decorative element or design feature.
“The architect incorporated a demicircle into the building’s design to create a sense of grandeur.”