Decade (noun)

1. A period of ten years.
2. A group of ten people or things.
3. A set of ten years within a century or larger time frame.
4. A period of ten years marked by a particular event or characteristic.
5. A sequence of ten in a series or progression.

Origin:

The word decade comes from the latin word "decas" which means a group of ten. this word was used to refer to a period of ten years.

Examples:

1. The past decade has been tumultuous.
2. The group was divided into decades.
3. The 1920s were a decade of prosperity.
4. A decade of hard work paid off.
5. The final decade in the countdown.