IPA: /dɪˈsɛn.i.əm/
KK: /dɪˈsɛn.i.əm/
A time span that lasts for ten years, also known as a decade.
The 1990s were a significant decennium for technological advancements.
Decennium is formed from "decem" (meaning ten) and "annus" (meaning year). The word refers to a period of ten years.
Think of 'decem' meaning ten and 'annus' meaning year — that's why decennium refers to a span of ten years.
No commonly confused words.