A suffix or prefix element relating to groups of nine, or a condition or quality occurring in sets of nine.
From Late Latin and Greek 'ennea-' (nine), derived from Greek 'ennea' meaning nine. This element appears in scientific and medical terminology to denote the number nine or patterns that repeat nine times.
You encounter 'ennia' hidden in scientific words like 'triennium' (a three-year period) and 'biennium'—the Latin 'enn-' root for nine is actually quite common in specialized vocabulary, even if you don't recognize it at first glance.
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