Yes, this would be perfect symmetry.
They have infinite lines of symmetry.
It not just has a line of symmetry; a perfect circle has an infinite number of lines of symmetry.
If you are talking about a perfect circle, it has wan infinite number if lines of symmetry. If you are talking about and actual lower case o, then the answer is two.
It has rotational symmetry of infinite order as well as an infinite number of axes of symmetry.
The only letter of the alphabet with infinite lines of symetry would be 'o' assuming it a perfect circle. Interestingly enough is also has infinite rotational symetry as well.
A sphere has an infinite number of lines of symmetry
There are infinite planes of symmetry in a cylinder in the same way that a circle has infinite lines of symmetry.
A circle has an infinite number of lines of symmetry. Any chord of the circle that passes through its center will be line of symmetry. Since there is an infinite number of chords, there is an infinite number of lines of symmetry.
Because the circle's diameter has infinite lines of symmetry
A cylinder has an infinite number of lines of symmetry (because a circle has an infinite number of lines of symmetry).
A circle has infinite lines of symmetry
There is an infinite number of lines across a circle that form two symmetric half-circles.