hemoglobin

noun

Etymology: Originally hematinoglobulin, from hematin (from Ancient Greek αἷμα (haîma, “blood”) + -in) + -o- + globulin (from Latin globus (“ball, sphere”) + -in).

1. The iron-containing substance in red blood cells that transports oxygen from the lungs to the rest of the body; it consists of a protein (globulin), and haem (a porphyrin ring with an atom of iron at its centre).