a hemoprotein composed of globin and heme that gives red blood cells their characteristic color; function primarily to transport oxygen from the lungs to the body tissues
"fish have simpler hemoglobin than mammals"
Initialism of horizontal branch.
hard black (describing a pencil that makes lighter marks than a grade B, but darker marks than a grade H pencil)
Initialism of Hansestadt Bremen. The German city of Bremen. (Used on licence plates and informally in other contexts.)