Relating to or lasting for a period of ten years.
From Latin decennium (ten years), combining decem (ten) and annus (year). The adjective form was created by adding the Latin suffix -alis to make it describe something that occurs every ten years or spans a decade.
Decennial celebrations are special because ten years is long enough that an entire generation of kids can reach new life stages—a baby born at the last decennial festival becomes a ten-year-old at the next one. This is why many cultures mark decennial anniversaries as major milestones!
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