A decagon is defined as a polygon with how many sides?

A decagon is a polygon that has ten sides. The prefix "deca-" originates from Greek, meaning ten. This is a standard definition in geometry, where polygons are classified based on the number of their sides, such as triangles having three sides, quadrilaterals having four sides, and so forth. Thus, a decagon is clearly identified as having ten sides, making this answer accurate and consistent with geometric terminology.