Microsecond (µs)
The microsecond, symbolized as µs, is one millionth of a second. This very short time is important in electronics, communication, and research. Microseconds are used to measure signal delays, computer speeds, and fast changes. As digital technology grew in the 1900s, measuring microseconds became necessary. Today, this accuracy supports applications such as fast trading, medical imaging, and satellite communications.
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.