This is the 3494th most frequent Swedish word.
decennium
A period of ten years; a decade.
In this sentence, 'decennium' is used in its basic form to refer to a time span of ten years.
Ett decennium består av tio år.
A decade consists of ten years.
Here, 'decenniet' is used in the definite form to denote a specific period of ten years.
Under det senaste decenniet har teknologin utvecklats snabbt.
During the last decade, technology has advanced rapidly.
In this example, 'förra decenniet' combines the word in its definite form with an adjective, indicating a specific past decade.