The word autologous is Greek in origin. The definition is exact 'autos' means self and 'logus' means relation. Thus, the meaning is 'related to self'. Autologous blood transfusion, which also is referred to frequently but incorrectly and imprecisely as auto transfusion, designates the reinfusion of blood or blood components to the same individual from whom they were taken. Homologous blood is blood or blood components, from another human donor, taken and stored for later transfusion as required.