The prefix 'sero' is derived from the Latin word 'SERUM, ' which means 'blood fluid.' It is commonly used in medical terminology to refer to blood fluid, such as SERUM, plasma, and lymph. SERUM is the clear liquid component of blood that remains after red and white blood cells and other cellular components are removed. Plasma is the liquid portion of the blood that contains proteins, hormones, and other substances. Lymph is a clear, slightly yellowish fluid that circulates through the lymphatic system and helps fight infection.