epicycle
/ˈepɪsaɪkl/noun
1- Geometry a small circle whose centre moves round the circumference of a larger one【几何】周转圆。
1.1
- historical a circle of this type used to describe planetary orbits in the Ptolemaic system〈史〉（用以描述托勒密宇宙体系中行星轨道的）本轮。
派生词
epicyclic
adjective词源
late Middle English: from Old French, or via late Latin from Greek epikuklos, from epi 'upon' + kuklos 'circle'.