A regular decagon
triangel
It is usually a regular polygon that has equal sides.
It is known as a regular polygon
There is no special name for that. However, if the sides are also equal, it is called a regular polygon.
A regular polygon
A regular hexagon.
A regular decagon
That is called a regular polygon.
infinitagon
A polygon with eight sides, regular or not, is an octagon. There isn't a special name for a regular octagon (other than "regular octagon").
It is not possible to name each polygon since there are infinitely many of them. There is no relationship between whether a polygon is regular and the number of sides or angles that it has. So, there is no way to determine, from its name, if a polygon is regular.
triangel
That is called a regular polygon.
It is usually a regular polygon that has equal sides.
If a polygon's sides are all of equal length, it is known as a regular polygon. (The measure of each of its angles will be the same as well)
pentagon