Changes

A polygon is a union of disjoint [[line segment]]s that is [[path-connected]].

A polygon is a union of disjoint [[line segment]]s that is [[path-connected]].

# no one's figured out how to make a one-sided polygon, but see [[Mobius strip]] and [[Klein bottle]]

# There is no such mathematical entity as a one sided polygon in a plane.  (For three dimensional analogies, see [[Mobius strip]] and [[Klein bottle]].)

# would be two overlapping [[line segment]]s

# As with the one-sided polygon, there is no such thing as a two-sided polygon.  (This would be two overlapping [[line segment]]s.)

# [[Triangle]] - see [[isosceles triangle]], [[equilateral triangle]], [[right triangle]]

# [[Triangle]] - see [[isosceles triangle]], [[equilateral triangle]], [[right triangle]]

# [[Square]] - a [[rectangle]] whose sides are all the same length

# [[Square]] - a [[rectangle]] whose sides are all the same length