Final answer:
The combining form of erythropoietin is 'erythro-', and the word root of erythrocyte is also 'erythro-', derived from Greek meaning red.
Step-by-step explanation:
The combining form of erythropoietin is erythro-, which refers to red or red blood cells, and poietin, which relates to the formation or generation of those cells. Erythropoietin (EPO) is a glycoprotein hormone that stimulates the production of erythrocytes (red blood cells) in the bone marrow, particularly when oxygen levels are low. Regarding the word root of erythrocyte, it is erythro- derived from the Greek word 'erythros' meaning red, emphasizing the red color due to hemoglobin within these cells.