ESR stands for erythrocyte sedimentation rate, which is a blood test that measures the rate at which red blood cells settle in a test tube over a designated period of time. This test is commonly used to detect inflammation or infection in the body. There are several synonyms for ESR, such as sedimentation rate, sedimentation test, erythrocyte sedimentation, and erythrocyte sedimentation rate test. Other synonyms include Westergren sedimentation rate, ESR test, and erythrocyte sedimentation rate blood test. These terms all refer to the same diagnostic tool for identifying inflammation in the body, and can be used interchangeably in medical settings.