A decade is a period of 10 years
A period of 100 years is called a century.
The word 'decade' is a noun, a singular, common, abstract noun; a word for a period of ten years or a group or set of ten, a thing.
A Period of ten years is called a decade.
A period of ten years is a decade.
A ten year period is a decade.
A period lasting ten years, or any ten year period.
The minimum period is two years and can be as long as ten years.