Rhombus Symmetry:
A rhombus is a quadrilateral with four sides of equal length. It is a special type of parallelogram where opposite sides are parallel and opposite angles are equal. In addition to these properties, a rhombus also has symmetry.

Symmetry:
Symmetry refers to an object's ability to have one or more lines or planes of symmetry. A line of symmetry divides an object into two equal halves that are mirror images of each other. In the case of a rhombus, it has two lines of symmetry that pass through its diagonals.

Lines of Symmetry:
The lines of symmetry in a rhombus are formed by its diagonals. A diagonal is a line segment connecting any two non-adjacent vertices of the rhombus. Since a rhombus has equal sides, its diagonals bisect each other at right angles. The point of intersection of the diagonals is the rhombus' center.

Symmetry about Diagonals:
When we say a rhombus is symmetrical about its diagonals, it means that if we fold the rhombus along any of its diagonals, the two halves will perfectly overlap each other. This is because the diagonals divide the rhombus into two congruent triangles. The line of symmetry is the diagonal itself.

Symmetry about Other Lines:
While a rhombus has other lines of symmetry, such as the line joining the midpoints of its adjacent sides or the perpendicular bisector of each of its sides, these lines do not divide the rhombus into congruent parts. Therefore, the rhombus is not symmetrical about these lines.

Conclusion:
In conclusion, a rhombus is symmetrical about each of its diagonals. Folding a rhombus along any of its diagonals will result in two identical halves. The other lines mentioned, such as the line joining the midpoints of its adjacent sides or the perpendicular bisector of each of its sides, do not divide the rhombus into congruent parts and therefore do not represent lines of symmetry for a rhombus.