for a short period of time. |- | microsecond || || One millionth of a second. Symbol is µs |- | millisecond || || One thousandth of a second. Shortest time unit used on stopwatches. |- | jiffy (electronics) ||~10-3 s | Used to measure the time between alternating power cycles. Also a casual term for a short period of time. |- style="background-color:rgba(255,255,0,0.25);" | second || 1 s || SI base unit for time. |- | minute || || |- | milliday || || Also marketed as a ".beat" by the Swatch corporation. |- | moment || ( on average) || Medieval unit of time used by astronomers to compute astronomical movements, length varies with the season. Also colloquially refers to a brief period of time. |- | kilosecond || || About 17 minutes. |- | hour || || |- | day || || Longest unit used on stopwatches and countdowns. |- | week || || Historically sometimes also called "sennight". |- | megasecond || || About 11.6 days. |- | fortnight || || 14 days |- | lunar month || || Various definitions of lunar month exist. |- | month || || Occasionally calculated as 30 days. |- |quarantine |40 d (approximately 5.71 weeks) |To retain in obligatory isolation or separation, as a sanitary measure to prevent the spread of contagious disease. Historically it meant to be isolated for 40 days. From Middle English quarentine, from Italian quarantina (“forty days”), the period Venetians customarily kept ships from plague-ridden countries waiting off port, from quaranta (“forty”), from Latin quadrāgintā. |- | semester || || A division of the academic year. Literally "six months", also used in this sense. |- | lunar year || || |- | year || || |- | common year || || 52 weeks and 1 day. |- | tropical year || ||Average. |- | Gregorian year || ||Average. |- | sidereal year || |- | leap year || || and |- | olympiad || || A quadrennium (plural: quadrennia or quadrenniums) is also a period of four years, most commonly used in reference to the four-year period between each Olympic Games. It is also used in reference to the four-year interval between leap years, for example when wishing friends and family a "happy quadrennium" on February 29. |- | lustrum || || In early Roman times, the interval between censuses. |- | decade || || |-