When does a parallelogram have fewer than four lines of symmetry?

A parallelogram has fewer than four lines of symmetry when it is not a rectangle or a square. Specifically, a general parallelogram, like a rhomboid, has only two lines of symmetry, which are the diagonals. In contrast, rectangles and squares have additional lines of symmetry, resulting in four lines for squares and two for rectangles. Thus, any non-rectangular parallelogram will have fewer than four lines of symmetry.