A partial character is a character for which we may lack a conclusion with respect to some of the taxa. In other words, the taxa are separated into three groups: those possessing the character, those not possessing the character, and a third group for which we have not yet formed a conclusion.
Partial characters are particularly useful when modeling the case of characters selected from genetic data (e.g., when genes are assigned to characters), as researchers have only just begun to sequence complete genomes from more than just a few species.
