A decade is a period of 10 years. The word is derived via French and Latin which means a group of ten. Decades may describe any ten-year period, such as those of a person's life, or refer to specific groupings of calendar years. 0-to-9 decade, the most widely used method for denominating decades is to group years based on their shared tens digit, from a year ending in a 0 to a year ending in a 9. A rarer approach groups years from the beginning of the AD calendar era to produce successive decades from a year starting in a 1 to a year ending in a 0, with the years 1–10 described as "the 1st decade", years 11–20 "the 2nd decade", and so on.