pus [L, corrupt matter] , a creamy, viscous fluid exudate that is the result of fluid remains of necrosis of tissues. It is usually pale yellow to yellow green, sometimes whitish, and sometimes bloody. Its main constituent is an abundance of polymorphonuclear leukocytes. Bacterial infection is its most common cause. The character of the pus, including its color, consistency, quantity, or odor, may be of diagnostic significance.
