半月形物

例句：

1. 1. The octopus has a biconcave shape that allows it to move through the water with ease.
   章鱼有一个双凹形状，这使得它在水中轻松移动。
2. 2. The moon is a semicircular object that orbits around the Earth.
   月亮是一个半圆形物体，绕地球运行。
3. 3. The scientist discovered a new type of biconcave object that could potentially be used in space exploration.
   科学家发现了一种新的双凹物体，可能被用于太空探索。