There's no difference because both words mean a 7 sided shape. However, "septagon" is an incorrect usage based on the supposition that the names of polygons are based on Latin, when in fact they are based on Greek. The correct name in English for a 7-sided, 2-dimensional figure is "heptagon."
Heptagon/Septagon it can be either
heptagon or septagon
It is an heptagon which is also a septagon because they both have 7 sides
A seven sided shape is called a heptagon.
A seven-sided shape (polygon) is called a heptagon.
A seven-sided shape is known as a "Heptagon"
That's a Heptagon or a septagon
A seven sided shape is called a heptagon or a septagon.......
Septagon or Heptagon = seven sided shape
a heptagon
A heptagon is a 7 sided polygon.
Heptagon/Septagon it can be either
Heptagon or septagon
heptagon or a septagon
A heptagon (or septagon).
heptagon or septagon
It is an heptagon which is also a septagon because they both have 7 sides