The Brainliest Answer!

A polygon is a closed plane figure which has three or more straight sides. A triangle has three sides and angles, so therefore, a triangle is an example of a polygon.

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ahhh ok so that, even the triangle is an example of polygon... but triangle can create only three angles, three sides and three vertex.... and that case polygon can create many angle, many sides, and many vertex....  thats why polygon from the greek word many angle....    thank you,.. :)   
A polygon is a plane figure that is bordered with line segments to create a closed figure.

A triangle is a three-sided polygon.
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