The bed and the chair are both furniture yet they both reside in different areas of the house.
Although the gym and auditorium are both large and hold many people they are designed for different things such as the gym for basketball and the auditorium for plays.
On the other hand, pins are used for sewing as needles, but needles are also used in a place of medicine.
Diamonds and iron many both be hard but only a diamond can break another diamond.