means The quality of being a distinct, separate person — the sum of traits, quirks, and character that make you you and not someone else.

from From Latin 'individuus,' meaning 'indivisible' or 'undivided' — 'in-' (not) plus 'dividuus' (divisible). The same root gives us 'individual,' which once meant simply 'that cannot be split.' The leap from 'unsplittable atom' to 'unique self' came as English thinkers shifted focus from the indivisible unit to the irreplaceable person — by an 18th-century coinage, 'individuality' carried the modern sense of a self too particular to be duplicated.