no idea, ive been looking for it myself.
It is when an object as one line of symmetry.
piece of string
A line of symmetry is a line through a shape. It shows that on either side of this line that the picture is exactly the same. There can be more than one line of symmetry in a shape.They are 'mirror images' when a shapes are divided by a lines of symmetry.
An object that has only one line of symmetry is said to have bilateral symmetry. This means that it can be divided into two equal halves along one axis.
bikateral symmetry
There is no specific name. It is one of the medians, angle bisectors and perpendicular bisectors: one set of these is coincident and is the line of symmetry.
You would call the group of shapes which has at least one line of symmetry symmetrical shapes. Stars, circles, and rectangles are considered symmetrical shapes.
One line of symmetry
A symmetrical shape is said to have line symmetry. A shape that has line symmetry can have one or more lines of symmetry
It has one line of vertical symmetry
C has 1 horizontal line of symmetry V & W have one vertical line of symmetry.
An isosceles triangle for example has only one line of symmetry