IPA: /ˈkoʊpstoʊn/
KK: /ˈkoʊpstoʊn/
A stone that is placed on top of a structure, often used as a finishing piece or decorative element.
The architect chose a beautiful copestone to complete the building's design.
Copestone → The word is formed from "cope" (from Old English *copa*, meaning to cover or top) and "stone" (from Old English *stan*, meaning rock or stone). A copestone refers to the stone that covers or caps a structure, often used in masonry.
Think of a 'cover' ('cope') that is made of 'stone' — a copestone is the stone that caps or covers a structure.