Meaning

noun an undivided or unbroken completeness or totality with nothing wanting

noun the smallest whole number or a numeral representing this number

noun the quality of being united into one

originEtymology tree Middle English unite English unity From Middle English unite, from Anglo-Norman, Old French unité, from Latin ūnitās, from ūnus (“one”) + noun of state suffix -itās, ultimately from Proto-Indo-European *óynos (“one, single”), hence distantly related to one and an. By surface analysis, unite + -y. Displaced native Old English ānnes (literally “oneness”).

Etymology from Wiktionary, CC BY-SA 3.0