词典释义：
a plane figure with three straight sides and three angles
三角形
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an equilateral triangle. 等边三角形。
a thing shaped like such a figure
三角形物
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a small triangle of grass. 一小块三角形草地。
a situation involving three people or things, especially an emotional relationship involving a couple and a third person with whom one of them is involved
（尤指情感上的）三角关系。
a musical instrument consisting of a steel rod bent into a triangle and sounded by being struck with a small steel rod
三角铁（打击乐器）。
a frame used to position the pool balls in snooker and pool
（摆放斯诺克和落袋台球撞球位置的）三角框。
〈北美〉 直角三角形三角板（绘图用具）。
(
〈史〉 （系缚士兵以鞭打的）三戟刑具。
a small brownish Eurasian moth of oak and beech woods
小型欧亚紫刺蛾（呈棕色，见于橡木及山毛榉林）。
"late Middle English： from Old French
