decennium/dɪˈsɛnɪəm/EtymologyFrom Latin decennium, from decennis (“10-year”) + -ium (suffix forming abstract nouns), from deciēs (“ten times”) + annus (“year”) + -is (suffix forming compound adjectives). Equivalent to decennial + -ium.decennium means Synonym of decade: a ten year period. Lexicurio rates it Rare gem — a strength score of 83 out of 100.nounSynonym of decade: a ten year period.“G.B. still has to cope with the heritage of approx. 20 years of consecutive Conservative reigns, just as you guys are getting your act together after almost a decennium of Enlightened Ronnie.”