The vital sign that measures the body's temperature is known as body temperature. It reflects the balance between heat produced by the body and heat lost to the environment. Normal body temperature typically ranges around 98.6 degrees Fahrenheit (37 degrees Celsius), although it can vary slightly from person to person and throughout the day due to various factors such as age, activity level, and time of day. Monitoring body temperature is crucial as deviations from the norm can indicate infections, illnesses, or other health issues. Medical professionals often assess temperature using oral, rectal, axillary, or tympanic methods for accuracy.