means Not seen, observed, or noticed — whether because it's hidden, overlooked, or simply absent from view.

from A transparent English compound: the prefix 'un-,' meaning 'not,' bolted onto 'seen,' the past participle of 'see.' Both halves are deeply Old English — 'un-' from a Germanic negating root shared across the family (German 'un-,' Dutch 'on-'), and 'sēon,' 'to see,' the ancestor of our verb. So 'unseen' is exactly what it looks like: the simple, ancient act of negating sight, a word that has quietly named the invisible for well over a thousand years.