Diphyodonty is a dental characteristic where an organism develops two sets of teeth over its lifetime: primary (deciduous) teeth and permanent (secondary) teeth. Most mammals, including humans, exhibit this trait, with the first set typically beginning to erupt in infancy and being replaced by the second set during childhood. This adaptation allows for growth and changes in jaw size as the organism matures. In contrast, some animals, like sharks, possess polyphyodont dentition, continuously replacing their teeth throughout life.