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| abstraction > mathematical concept > geometrical object > conic section > ellipse > circle > great circle > hour circle | 
| hour circle comparison table | ||
| Subject | is a kind of | has definition | 
|---|---|---|
| great circle | circle | A circle on the surface sphere whose diameter equal to the diameter of the sphere. | 
| hour circle | great circle | A great circle passing through the celestial poles - i.e., perpendicular to the celestial equator. | 
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