Tierce, also known as third, is a unit of time equal to 1/60 of a second. One minute is 3600 tierces and one hour is 216000 tierces. The unit comes from the Latin word terce, meaning "third". This unit is rarely used, and millisecond is used instead to specify the period less than a second. One tierce is equal to 16.6 milliseconds. A blink of an eye lasts from 18–24 tierces.