A platelet is one of the very small, flat, round pieces in your blood. When you cut yourself, platelets help the blood become solid, so a clot can form and you stop bleeding. They are not the same as red cells, which carry oxygen, or white cells, which fight illness. Doctors and biology teachers use this word; in ordinary talk people usually just say your blood clots, without naming them. They were called platelets because under a strong lens they look like tiny plates.

血小板