Is a oval a irregular polygon?

Answer 1

It's an irregular shape, but not an irregular polygon.

Addendum to the above answer:

Hopefully most of us will accept the above answer as correct, since it is correct for any practical or usefull purpose. However, if you are interested in pure theoretical geometry (which appears to be the case of the asker of the above question), consider the following.

A "polygon" is, by definition, a multiple-sided, multiple-angled plane figure. An oval, like a circle, at first glance, appears to have only one continuous side and no angles, so it does not qualify as a polygon.

However, if you had a polygon with 100 equal sides and 100 equal angles, it would look somewhat like a circle, and if it had 1000 it would look even more like a circle. If it had 10 million sides and angles, it would be, for practical purpose, a circle...even though it is still a polygon (a multiple-sided figure).

So a true circle could be considered to be a regular polygon with an infinite number of equal sides and a corresponding number of equal angles

An oval, on the other hand, would have an infinite number of sides, but would have ever-changing angles between them, making the oval an irregular polygon.