What is the definition of a hexagon?

A plane figure (2-dimensional) of 6 sides.

Remember from Latin the prefix of the Word indicates the number of sides.

'Poly = Many

Tri = 3

Tetra/Quad = 4

Penta = 5

Hexa = 6

Hepta = 7

Octa = 8

Nona = 9

Deca = 10

The suffix 'gon' indicates that it is a plane 2- dimensional figure.