What is rare definition?

Rare means something that is not commonly found or occurring, unusual or uncommon. It can also refer to something that is extremely precious or valuable. In medical terms, a rare disease is a condition that affects a small percentage of the population. In chemistry, rare elements are elements that occur in very small quantities or are found in only a few places on Earth. Overall, rare refers to something that is infrequent, special and often considered highly prized.