The state or condition of being dominant; supremacy or commanding influence.
From 'dominant' (from Latin 'dominans', present participle of 'dominari' meaning to rule) + '-cy' (forming abstract nouns). Related to the older word 'dominance,' dominancy is a less common variant emphasizing the abstract quality of rule.
Both 'dominance' and 'dominancy' mean the same thing, but 'dominancy' is rarely used today—it's a linguistic fossil showing how English speakers once had more freedom to create similar-sounding noun variants, before standardization made certain forms 'standard' and others archaic.
Complete word intelligence in one call. Free tier — 50 lookups/day.