Plasma: the liquid portion of blood is called plasma.
Plasma contain 90% water, 7% plasma proteins and 3% other subatances.
Plasma proteins are Serum Albumin, Serum Globulin, Prothrombin and Fibrinogens.
Serum: Fibrinogen free plasma is called serum.
NOTE: FIBRINOGEN PRESENT IN PLASMA IS RESPONSIBLE FOR COAGULATION OF BLOOD AFTER COMING OUT OF THE BLOOD VESSELS HENCE FOR CLINICAL ANALYSIS OF BLOOD LIKE COUNTING HAEMOGLOBIN COUNT OR OTHER ANALYSIS SERUM IS MOSTLY USED BECAUSE IT DOSENOT COAGULATES DUE TO ABSENCE OF FIBRINOGEN.