What is the name of the liquid part of blood?

The name of the liquid part of blood is plasma.

Plasma is the pale yellow, liquid matrix in which red blood cells, white blood cells, and platelets circulate. It makes up roughly 55% of whole blood and is composed mostly of water, with dissolved proteins, salts, nutrients, hormones, gases, and waste products. By carrying these substances, plasma helps maintain blood pressure, distribute heat, and transport materials throughout the body.

Several major plasma proteins have specialized jobs. Albumin helps maintain osmotic pressure, antibodies support immune defense, and fibrinogen contributes to clot formation. Plasma also carries carbon dioxide from tissues toward the lungs and transports nutrients such as glucose.

A common mix-up is plasma versus serum. Serum is the liquid left after blood has clotted, so it lacks most of the clotting protein fibrinogen. Cytoplasm is the material inside cells, while lymph is a separate fluid of the lymphatic system. Plasma is also used in transfusion medicine and in laboratory testing.