What does the phrase 'postmortem lividity' refer to?

The phrase 'postmortem lividity' refers to the color change in the skin after death, specifically the pooling of blood in the lower parts of the body due to gravity. This phenomenon is caused by the cessation of circulation and can result in purplish-blue discoloration of the skin in areas where blood has settled. This process begins within minutes of death and can help forensic investigators determine the position of the body at the time of death, as well as the time frame in which death occurred.

The other terms listed relate to different postmortem processes. Muscle stiffness after death is known as rigor mortis, which occurs after lividity and is characterized by the stiffening of the body's muscles. Gaseous buildup in the body occurs due to decomposition, leading to bloating, while change in temperature of the body refers to algor mortis, which involves the cooling of the body after death. Each of these terms describes different aspects of the postmortem interval and physiological changes, but postmortem lividity specifically pertains to the change in skin color due to blood pooling.