A period of 20 years is called a “score.” This term is most famously used in the phrase “four score and seven years ago” from Abraham Lincoln’s Gettysburg Address, where “score” refers to a period of 20 years.
Here are a few more terms related to periods of time:
- Decade: A period of 10 years.
- Century: A period of 100 years.
- Millennium: A period of 1,000 years.
- Eon: A long period of time, often used to describe geological time spans of millions or billions of years.
- Generation: Typically a period of 20–30 years, representing the time it takes for one generation to be born and grow up to have children.
In everyday language, people don’t often use “score” outside of historical or poetic contexts, but it still refers specifically to 20 years.