What is the name of a polygon with 9 sides?

The name of a polygon with nine sides is indeed a nonagon. This term is derived from the Latin word "nonus," meaning nine, combined with the suffix "-gon," which indicates a geometric figure. In geometry, the number of sides of a polygon determines its classification; thus, a nonagon is specifically defined as a nine-sided polygon.

In context, a decagon is a polygon with ten sides, a hexagon has six sides, and a pentagon has five sides. This highlights the specific nature of polygon naming conventions, where the prefix typically refers to the number of sides. Therefore, nonagon accurately describes a nine-sided polygon, affirming the correct answer in this instance.