adjective

1. without legal force; not binding; invalid: usually in the phrase null and void
2. amounting to naught; nil
3. of no value, effect, or consequence; insignificant
4. Math. designating, of, or being zero, as
   1. having all zero elements null matrix
   2. having a limit of zero null sequence
   3. having no members whatsoever null set

Etymology: MFr nul < L nullus, not any, none < OL *n(e) oin(o)los, not a one < ne, not (see no) + dim. of oinos < IE *oinos: see one