DECENNIUM
decade, decennary, decennium
(noun) a period of 10 years
Source: WordNet® 3.1
Etymology
Noun
decennium (plural decenniums or decennia)
A period of ten years.
Usage notes
Although decade may be taken as any group of ten years, it is commonly restricted to the informal ten-year periods of the calendar whose last digits run from 0 to 9. Decennium has no such restriction.
Synonyms
• decenniad
• decennary
• (in some contexts): decade
Source: Wiktionary
De*cen"ni*um, n.; pl. Decenniums, L. Decennia. Etym: [L.]
Definition: A period of ten years. "The present decennium." Hallam. "The
last decennium of Chaucer's life." A. W. Ward.
Source: Webster’s Unabridged Dictionary 1913 Edition