"plane figure having ten sides and angles," 1630s, from Modern Latin decagonum, from Greek dekagonon, from deka "ten" (from PIE root *dekm- "ten") + gōnia "corner, angle" (from PIE root *genu- (1) "knee; angle"). Related: Decagonal.
deca-
decade
decadence
decadent
decaffeinate
decagon
decahedron
decal
Decalogue
Decameron
decamp
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