If you take a circle for example, a line of symmetry is any line that can go through that circle and if you fold the circle in half it will be equal.
So a line of symmetry is a line that you divide any shape in half with and have both halves be the same.
None.
Yes.
Infinite lines of symmetry
2
None.
Yes.
An ellipse has two lines of symmetry.
3
Yes.
It has one line of symmetry
An irregular 7 sided heptagon normally has no lines of symmetry depending how it is constructed.
A prism and cylinder both have edges and verticies and faces and lines of symmetery.