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A decade is a period of 10 years. The word is derived (via French and Latin) from the Ancient Greek: δεκάς, romanizeddekas, 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.


Any period of ten years is a "decade".[1][2] For example, the statement that "during his last decade, Mozart explored chromatic harmony to a degree rare at the time" merely refers to the last ten years of Mozart's life without regard to which calendar years are encompassed. Also, 'the first decade' of a person's life begins on the day of their birth and ends at the end of their 10th year of life when they have their 10th birthday; the second decade of life starts with their 11th year of life (during which one is usually referred to as being 10) and ends at the end of their 20th year of life on their 20th birthday; the third decade, referred to as being in one's twenties (20s), starts with the 21st year of life (during which one is referred to as being 20) and ends at the end of the 30th year of life on their 30th birthday; subsequent decades of life are described in a similar way by reference to the tens digit of their age.

There are two methods of demarcating specific groupings of calendar years into decades.

Cardinal decade[edit]

The most frequently used convention for denominating decades is to group years cardinally with respect to the anno Domini-before Christ convention, i.e. based on their shared tens digit – for example, the period from 1960 to 1969, the nineteen-sixties (1960s), is one such grouping.[3][4] Sometimes, only the tens part is mentioned (60s or sixties), although this may leave it ambiguous as to which century is meant. Following this convention, a new decade begins when the tens digit of a numerical year changes (for example, the 1970s began when 1969 ended and 1970 began) and ends on the last day of the next year ending with a nine.[5]

Ordinal decade[edit]

A rarer approach is to group anno Domini-before Christ years ordinally, i.e. in such a manner that each decade can be described as 'the Nth decade since the start of the common era' - for example the period from 1981 to 1990 would be considered the "199th decade". This method can also be used to describe any other period divided into decades, such as 'the 1st decade of the 1900s', or 'the fourth decade of life.' The last year of any ordinal decade ends in a year that corresponds to the decades title (For example, the year 2010 was the final year of the 201st decade).

Public usage of the two methods[edit]

Particularly in the 20th century, cardinal decades came to be referred to with associated nicknames, such as the "Swinging Sixties" (1960s), the "Warring Forties" (1940s) and the "Roaring Twenties" (1920s). This practice is occasionally also applied to decades of earlier centuries; for example, referencing the 1890s as the "Gay Nineties" or "Naughty Nineties".

A YouGov poll was conducted on December 2, 2019, asking 13,582 Americans whether the following decade would begin on New Year's Day 2020 or New Year's Day 2021. Results show that 64% of Americans answered the next decade will begin on January 1, 2020, and will end on December 31, 2029 (the cardinal range). 19% of the Americans surveyed replied they are unsure, while 17% answered the next decade will begin on January 1, 2021, and will end on December 31, 2030 (the ordinal range).[6]

Ordinal vs cardinal usage
Year 1 2 3 ... 8 9 10 11 12 13 ... 18 19 20 ... 2000 2001 2002 ... 2008 2009 2010 2011 2012 ... 2018 2019 2020 2021 2022 ... 2028 2029 2030
Ordinal decade 1st decade 2nd decade ... 201st decade 202nd decade 203rd decade
Cardinal decade 0s 10s ... 2000s 2010s 2020s ...

See also[edit]


  1. ^ "Oxford Dictionaries". Retrieved 19 January 2015.
  2. ^ "Webster dictionary definition of "decade"". Archived from the original on 2013-06-05. Retrieved 2009-12-31.
  3. ^ "The OWL at Purdue: The Apostrophe". Retrieved 5 July 2019.
  4. ^ "1960s". Memidex/Wordnet Dictionary/Thesaurus. Retrieved 2011-08-18.
  5. ^ "Confirmation that 2019 concludes warmest decade". Met Office. Retrieved 2020-01-18. 2019 concludes the warmest ‘cardinal’ decade (those spanning years ending 0-9)
  6. ^ "In recent years, there has been debate around when a decade begins and ends. When do you think the next decade will begin and end?". YouGov. Retrieved 21 December 2019.

External links[edit]