The 2020s and the Third Decade Are Not the Same Ten Years
A decade is a period of ten years. Whether it starts in a zero year or a one year depends on what you are counting.
A decade is a period of ten years. Two systems compete and both are right in their own terms: culturally, the 2020s run from 2020 to 2029, because they share a digit. Arithmetically, the third decade of the century runs from 2021 to 2030, because there was no year zero. Arguments about this recur every ten years and settle nothing.
- A period of ten years. *The last decade.*
- A group of ten. *A decade of the rosary.*
- Decadal — occurring every ten years. *Decadal variation.*
Word forms
| Form | Word | Example |
|---|---|---|
| Noun | decade | A whole decade. |
| Plural | decades | Three decades. |
| Adjective | decadal | Decadal cycles. |
| Related | century | The last century. |
| Related | decimal | Decimal places. |
How it is used in a sentence
- The 1960s were a turbulent decade.Cultural grouping.
- The century's third decade began in 2021.Arithmetic counting.
- A decade of the rosary is ten beads.Religious use.
Periods of time
- Decade — ten years
- Score — twenty, of anything
- Generation — loosely twenty-five to thirty years
- Century — one hundred years
- Millennium — one thousand years
From Latin *decas*, from Greek *dekas*, a group of ten, from *deka*, ten — the same root as *decimal* and *decimate*.
When did the 2020s start?
In 2020 if you mean the years sharing that digit, which is the usual cultural sense. In 2021 if you are counting decades from year one.
Why is there no year zero?
Because the calendar was designed before zero was in general European use, so year 1 BC is followed directly by AD 1.