key·stone 
(kēstōn′)
(kēstōn′)n.
1. Architecture A wedge-shaped stone at the top of an arch, often larger or more ornamented than the other voussoirs. Also called headstone.
2. The central supporting element of a whole.
| 单词 | keystone |
| 释义 | key·stone (kēstōn′)n. 1. Architecture A wedge-shaped stone at the top of an arch, often larger or more ornamented than the other voussoirs. Also called headstone. 2. The central supporting element of a whole. |
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