Millisecond (ms)
The millisecond, symbol ms, is one-thousandth of a second. It is important to time very short periods. The millisecond, a unit of measurement in the metric system, is used in science, computers, and engineering. It measures speeds and response times in digital devices. People’s reaction times are often measured in milliseconds, making it useful in medicine, sports, and psychology. Its accuracy helps capture events that happen too fast for the eye to see.
Year (yr)
The year, symbol yr, is the time Earth needs to go around the sun—about 365.242 days. People have tracked years for farming and religion for a long time, creating calendars. The Julian and then the Gregorian calendars made the year’s length more exact by adding leap years. Today, the year is used everywhere for history, science, work, and culture. Years are closely linked to how people see seasons and life’s cycles.