/ ˈdekəgən; NAmE -gɑːn/ noun
( geometry ) a flat shape with ten straight sides and ten angles
► dec·agon·al / dekˈægənəl; NAmE / adjective
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WORD ORIGIN
mid 17th cent.: via medieval Latin from Greek dekagōnon , neuter (used as a noun) of dekagōnos ten-angled.