The most common term is "nonagon", though technically "non-" is a Latin prefix. The purely Greek word for it is "enneagon." But no one really uses this term , so you're safe with "nonagon."
A 9 sided polygon is a nonagon
A 9 sided polygon is a nonagon
this is called a nonagon
A nonagon
A nonagon
a nonagon
A 9 sided polygon is a Nonagon.
Nonagon
a nine sided polygon is called a nonagon.
A nine sided shape or polygon is called a nonagon.
The name of a 9 sided polygon is Nonagon.
A five sided polygon is called a pentagon because pentagon means five sided polygon I think.