Decade (dec) - Unit Information & Conversion

Definition

A decade is a unit of time equal to 10 consecutive years. It is commonly used to group years for historical, cultural, or statistical analysis, often referring to periods like the 1980s or 2010s.

History

The term "decade" originates from the Ancient Greek word "dekas" (δέκας), meaning a group of ten, which passed into Latin as "decem" and then into English. Its application specifically to a ten-year period became standard alongside the development and use of calendar systems for tracking longer spans of time.

Common Uses

Decades are frequently used for:

• Historical periods: Referring to specific ten-year periods, typically starting with a year ending in '0' (e.g., the 1990s refers to the years 1990-1999).
• Trend analysis: Discussing cultural, social, economic, or political trends that characterize a ten-year span.
• Anniversaries: Marking significant anniversaries known as decennials (10th anniversaries).
• Data analysis: Grouping data in demographic studies, historical analysis, and long-term planning.

Unit FAQs

How many years are in one decade?

A decade is defined as exactly 10 years.

How are decades typically named or referred to?

Decades are commonly referred to by the century and the tens digit of the years they encompass, such as "the 1980s" (1980-1989) or "the 2020s" (2020-2029). The first decade of a century (e.g., 2000-2009) is sometimes called "the noughties" or "the aughts".

Is the decade an SI unit?

No, the decade is not a unit within the International System of Units (SI). The base SI unit for time is the second. While widely used in historical and cultural contexts, scientific measurements typically use seconds, years (often Julian years for consistency), or larger multiples like kiloyears (kyr) or megayears (Myr).