Which figure has 7 sides?

The polygon of seven(7) sides is named an 'HEPTAGON'.

For the given number of sides of other polygons, the prefix is

3 = tri ( trigon / triangle)

4 = tetragon ( rectangle/ quadrilaterial)

5 = penta

6 = hexa

7 = hepta ( as above)

8 = octa

9 = nona

10 = deca.