lunette
/ljuːˈnet/noun
1- something crescent-shaped, in particular月牙形的物体, 尤指：
1.1
- an arched aperture or window, especially one in a domed ceiling（尤指在建筑物穹顶上的）弧形空间; 弧形窗。
1.2
- a crescent-shaped or semicircular alcove containing something such as a painting or statue（内有画或雕像的）新月形（或半圆形）壁龛。
1.3
- a fortification with two faces forming a projecting angle, and two flanks眼镜堡。
1.4
- Christian Church a holder for the consecrated host in a monstrance【基督教】（圣体匣中搁圣体的）圣体托架。
1.5
- a ring fixed to a vehicle, by which it can be towed（车辆的）牵引环。
词源
late 16th cent. (denoting a semicircular horseshoe)： from French, diminutive of lune 'moon', from Latin luna.