Can you find the area of a rhombus if you only know the lengths of the sides?

no, one other piece of information , such as one of the angles or one of the diagonals must be given.

Many years back on Sesame Street, Oscar the Grouch took a rectangle and squished it, so its angles were no longer 90°. He then called it a wrecked-angle.

Notice that if you start with a square and squish it, it becomes a rhombus, and its are is definitely smaller.