Definition of red blood cell
:any of the hemoglobin -containing cells that carry oxygen to the tissues and in mammals are typically biconcave disks which lack a nucleus and cellular organelles and are formed from nucleated cells of the red bone marrow
Note:
The number of red blood cells ranges from four to six million in each cubic millimeter of normal human blood. The red color of blood is due to the presence of hemoglobin within the red blood cells.
— called also
erythrocyte; compare white blood cell 
