A polygon (flat shape) with exactly ten straight sides and ten angles.
From Greek deca- (ten) + -gon (angle or side). The word combines the Greek prefix for the number ten with the geometric suffix for polygons, following the same pattern as pentagon, hexagon, and octagon.
Decagons appear all over nature and design—some flowers have 10 petals, and the shape shows up in architecture and art because it's complex enough to look interesting but ordered enough to feel balanced!
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