The Collaborative International Dictionary
Decenniums
Decennium \De*cen"ni*um\, n.; pl. Decenniums, L. Decennia.
A period of ten years. ``The present decennium.''
--Hallam.
``The last decennium of Chaucer's life.''
--A. W. Ward.
Wiktionary
decenniums
n. (plural of decennium English)