Why are potato ginger and onion not considered as roots?

Potatoes, ginger, and onions are not classified as true roots because they are modified plant structures. Potatoes are tubers, which are swollen underground stems that store energy. Ginger is a rhizome, a type of underground stem that grows horizontally and produces shoots and roots. Onions, on the other hand, are bulbs, which are storage organs consisting of a short stem surrounded by fleshy, modified leaves.