biennium

[bahy-en-ee-uh m] /baɪˈɛn i əm/
noun, plural bienniums, biennia
[bahy-en-ee-uh] /baɪˈɛn i ə/ (Show IPA)
1.
a period of two years.
Origin
1895-1900; < Latin, equivalent to bi- bi-1 + -enn- (combining form of annus year) + -ium -ium
Word Origin and History for biennium
n.

"space of two years," by 1851, from Latin biennium "two years, a period of two years," from bi- + annus "year" (see annual). For vowel change, see biennial.