blood type definition
One of many groups into which a person's blood can be categorized, based on the presence or absence of specific antigens in the blood. Blood type is inherited.
Note: Blood transfusions can be given only between donors and recipients who have compatible types; if the types are not compatible, the blood of the recipient forms antibodies against the blood of the donor. There are four basic groupings — A, B, AB, and O — and within these groupings, the Rh factor may be present or absent.