decennium

noun

1. (rare)Synonym 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.”

   “Christian leaders refused even to *look* through Galileo's telescope (as a matter of fact, the Vatican cleared Galileo's name only as late as in the previous decennium).”