semi·cir·cle /ˈsɛmiˌsɚ/
半圓形
Sem·i·cir·cle n.
1. (a) The half of a circle; the part of a circle bounded by its diameter and half of its circumference. (b) A semicircumference.
2. A body in the form of half of a circle, or half of a circumference.
3. An instrument for measuring angles.
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semicircle
n : a plane figure with the shape of half a circle [syn: hemicycle]